Tape Project Forum

General Category => General Discussion => Topic started by: ceved on August 24, 2008, 07:39:26 pm

Title: Beginners Guide to Tape Recorder Basics
Post by: ceved on August 24, 2008, 07:39:26 pm
Welcome novices and perts alike.
The purpose of this thread is to disseminate basic information and knowledge to those individuals new to the tape recording format or those wishing to refresh their expertise from earlier encounters with the rtr format.
If you feel as though you don't quite know what you are doing, how to do what you need/want to do, or not quite sure what a term or phrase means then this is the thread for you.

Yes, this is Tape Recorders 101.
We are trying to establish a data resource contained in one thread so that all the information/questions novices are likely to need/ask will be easy to locate whether it has to do with how to add leader, demagnetizing, to what 'tails out' means let alone how to do it, prepping your latest used tape for its' first spin. In other words everything.

While we novices may have the questions, we need you experts to throw us a life perserver in the way of an answer or a link.  So if you know the ropes, please lend a hand as it can be very exasperating when you are just starting out.

To get things going, I would like to bring to your attention a nifty little book I recently purchased on Ebay entitled 'How to Make Good Tape Recordings'
The Author is C.J. Le Bel and the publisher is Audio Devise Inc. copyright 1958.
It is really a basic primer and would be a wonderful acquisition for your library especially if you are just starting out.
If I can figure out how to scan the pages without breaking the spine, I will be happy to make it available for posting here on the TP.
Do you have a resource that you know of or own which would be helpful to a TP novice?

In summation if you have a question, problem, curiosity about any aspect of 'taping', and do not know where to turn?
All those 'stupid' questions you were reluctant to ask are not only welcome, but expected here.
Aunty Em there really is no place like home!
This is your thread!

Title: Re: Beginners Guide to Tape Recorder Basics
Post by: ironbut on August 24, 2008, 10:38:17 pm
I found a copy of "How to Make Good Tape Recordings" by googling it. Anyone interested in a copy can find it here;
I've had great results finding out of print stuff over on Amazon too.
If any of the other members would like to jump in and write a bit about tape recorder basics, be my guest. Since we are trying to give new users their wings as soon a possible, please try and link to illustrations whenever possible. Remember, you can always edit your posts at a latter date. So if you're like me, and know that you've seen something that you really want to add, don't sweat it (you may have noticed that almost all my longer posts have been edited). And if any of you know that myself or others have made mistakes in our advice, please correct us. We want this stuff to be very accurate. If you feel weird about correcting someone publicly, PM them (I don't know about other members, but I use the Private Message feature all the time). There will be things that are peculiar to specific machines which no one without that machine will know about. That's important to include too.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: jgbeam on August 25, 2008, 08:18:35 am
This is the beginning of a great thread but could be missed by many if it remains under Tape Project Albums.  It deserves its own title, if not a dedicated section.  I, too, need all the help I can get.
Title: Heads, where the rubber hits the road
Post by: ironbut on August 26, 2008, 12:18:34 am
I thought that I'd start this guide with a discussion of the heads since it's the interface between them and the tape that makes it all happen. It's also this interface that makes the difference between a poor performing machine and the very best. Almost every consumer or pro-sumer (machines that attempt to bridge the gap between consumer and professional machines) include recording and playback facilities. Most are 3 head machines and the usual order of the heads (in the direction of the tape during playback) is erase, record and playback. This order is done for a reason. When recording,  erase head clears or deletes any sound that's already on the tape so the record head can imprint the music that you want on the tape. The playback head is last in line so you can hear or monitor what's just been recorded on the tape.
For this post, we'll concentrate on the playback head only since it's the only one that's important for playing the Tape Project tapes.

Track configurations on heads
By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-08-25 photo courtesy of Richard Hess 2001 http://www.richardhess.com/tape/index.htm
Ignoring the embedded text regarding the 8 and 16 track machines( on another photo not included) we can see a good illustration of how the tracks on a four channel machine are spaced. The head in the middle is the record head and the one on the right is the playback head.
These are 4 channel heads as opposed to stereo which of course is 2 channel. This head assembly would record and playback in one direction only on the entire width of the tape. If we were to number the tracks(channels) 1-4 starting with the top and counting down keep an eye on tracks 1 and 3. Most of the older tapes that you buy on eBay that are labeled 4 track (1/4 track) stereo. If we were to superimpose a photo of the heads of a 1/4 track machine you'd see that the tracks on those heads would line up with tracks 1 and 3. The one that lines up with track 1 is always the left channel and the one that lines up with track 3 is aways the right channel (this is important to remember for chasing down pesky problems so just remember that the top track is always the left channel in 1/4 track stereo ( I usually refer to 4 track stereo as 1/4 track to keep it clear that I'm not talking about 4 channel). When you play a 1/4 track tape and finish side one, you flip the tape over. So when you play side two, you're playing what was tracks 2 and 4. That's why a 1/4 track head's track marks look a little offset toward the top with a big space between them. So, a 1/4 track stereo tape does indeed have 4 tracks, but the it's divided into 2 tracks in one direction and 2 in the other direction. A 1/4 track head only has 2 tracks and relies on you to turn the tape over to reveal the other two tracks. If the tape were to slip up or down (on a 1/4 track tape), the other two tracks would be audible which would be pretty obvious because their sound would be in reverse. Of course, if the heads were to shift up or down it would also start to playback the other two tracks in reverse. As you might guess, the adjustment of the head up and down is important. Strangely enough, this head adjustment is called "height".

Next 1/2 track heads

Title: Re: Beginners Guide to Tape Recorder Basics
Post by: docb on August 26, 2008, 09:42:22 am
Where the rubber hits the road? Dude, maybe you need new pinch rollers...
Title: Heads- 1/2 track
Post by: ironbut on August 26, 2008, 11:12:05 pm
To continue on with our discussion of heads, the picture below is of the heads on a 1/2 track stereo Sony APR 5000 series machine. It has a somewhat specialized head assembly. At first we'll focus on the three heads we already know. Once again, we find the same configuration of erase head>record head>playback head (following the direction the tape travels in play-left to right). Although it's a little harder to see the tracks on the record and playback heads you can see a lighter space in the very middle of the head. This is the border between the two tracks. This is the format that the Tape Project tapes are recorded in. Once again, the left channel is on top (track 1) and the right channel is below the border. So, as you can see, the two tracks take up the full width (except for the border between them).
Because the 2 tracks take up the entire width, the tape is unidirectional and unlike the 4 track stereo tapes that were mentioned in the first "heads" posting, if you were to flip the tape and play it, it would be in reverse (which is pretty fun about once). These tapes are best stored in what we call "tails out". All that means is that the tape is put away (without  rewinding it/flipping it or any other tom foolery), just the way it is after playing it till the end. It's actually the most convenient way to deal with these tapes and good for the tapes to boot. Of course this means that before playing a "tails out" tape, you need to rewind it onto an empty reel on the left reel turntable. We'll get into tape storage/handling and care in a later post.
By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-08-25
 What's particularly cool about this photo is all the other parts in a head assembly are clearly labeled.
Starting on the far left is a metal guide. The guides do just what they say, but this is another case of less is better. The less guiding the guides have to do the better the sound. Any contact that the tape has with a guide creates friction and this friction creates noise. Minimizing this guiding is the result of proper adjustment done on the entire machine. This is a part of what Doc ( the wise guy dude ) does when he optimizes the tape path with his modifications.
After the guide is a "time code" head. It applies a track into that border between the 2 tracks to sync sound to film or whatever. For the purposes of this discussion that's all I'll say about it (pretty easy since that's about all I do know!).
After that comes the 2 track erase head and then the first in a pair of lifters. The lifters "lift" the tape above the heads during fast forward and rewind and retract during play. When the lifters are retracted the tape moves across the heads and through the guides to allow the heads to "read" the information on the tape. When engaged, the lifters prevent wear on the heads. All adjustments of the heads are done without the lifters engaged.
The idler is only present on some machines although one can be added if there's room. The idler on this machine is used for sonic improvement and the use of these devices will be discussed when we talk more about tape handling and the effects it has on sound.
The last device on this head assembly that we haven't addressed before is the tape sensor. There are several different types of sensors (this one appears to be opto-electric) but they all have the same basic function. They stop the machine at the end of a tape from fast forward, rewind or play when there is no tape breaking a light/sensor interaction (as in this one) or releasing a spring loaded arm (as most consumer/prosumer machines have). When you work on a machine you can "fool" any sensor into thinking there's tape present (and you'll be able to engage play, rewind, fast forward) with a piece of tape either blocking the light sensor or holding the mechanical arm up.
If you look at the top of the head assembly, you'll notice a series of labeled holes. These are for access to the head adjustments. One of the main adjustments for a playback head is to keep the vertical orientation as close to 90 degrees as possible or needed. Imagine a tape with a quick, regular pulse recorded on it. If you could see it on the tape, you'd have a pattern that would look a little like a bar code down the length of the tape with this recording on it. If the playback head was tilted , you could see that part of each track of the head, would be "reading" this pulse before it should, while other parts of the head will be "reading" the pulse after it should be. If the tilt was extreme enough you'd also get pre and post echoing from the other track as it read it's track before or after the other. As you might guess, very slight tilts would result in phase issues with transients and images smeared. Adjusting the heads to eliminate any "tilt" is obviously central to the qualities of the outputs sound. This adjustment is called azimuth.

Once again, the photo is courtesy of Richard Hess 2001 http://www.richardhess.com/tape/index.htm
Title: Heads- Pt.3 Other formats
Post by: ironbut on August 27, 2008, 11:09:20 pm
By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-08-26
OK, so you guys have seen pictures of the most often seen formats (1/4 track stereo and 1/2 track stereo). If you've studied the text, here's a little quiz. What is the format of the the machine whose heads are shown above? Well, here's some hints. The tracks are the orange colored slots and since there are two on each head, it's stereo. Another clue is that there's plenty of room between these tracks to put another track in between. From those two observations we can figure that this is probably a 1/4 track stereo machine. The main difference between this set up and what is usually seen on most 1/4 track stereo machines is the fourth head. One thing I haven't mentioned that would help, is that playback heads usually have a "shield" around them to reduce picking up hum from the rest of the machine (the record and erase heads are putting out a signal so they don't need shields). So the first and last heads are both playback. There are two main types of machines that have more than one playback head, a multi format machine such as the Technics RS1500 series and the Otari 5050 mk1 and 2 and auto reverse decks. This is one of the latter since as you can see, both of the playback heads have the same track width. The shields make it difficult to see the offset of the tracks but as I keep saying, the second head must be the erase head, the third is the record head and the fourth is the playback head. With an auto reverse deck, rather than having to flip the tape to play the "B" side, the machine plays backwards and switches which head is being accessed.  Even though we can't really see the opposite offset of the two playback heads, it must be there.
On one of the Technics machines (which playback in 1/2 and 1/4 track stereo) it depends on which model (1500 or 1506) on which head playback is first and which is last. A 1500 records in 1/2 track stereo and plays back in 1/2 and 1/4 track stereo. Once again the old rule applies. Erase>Record>Playback. If it records in 1/2 track stereo than the 4th head "must" be the 1/2 track playback head. If it's a 1506 which records in 1/4 track stereo, than the 4th head "must" be a 1/4 track playback head.
There are machines that were pretty popular in the 1970-80's that throw a monkey wrench in this. Teac created quite a stir when they released a machine called the 3340s. The "S" stands for sync and the 3340s was a 4 channel machine (that's 4 channels in one direction like the head assembly shown in the first picture in the heads posts). Four channels was nothing new but this machine allowed each channel to be recorded at a time and the remaining channels could be added (overdubed) one at a time later. This doesn't seem too revolutionary since it would seem that it would only require switching of each record channel as you overdub each channel. If you look at the picture above and look at heads 3 and 4 (record and playback) you will see that there's a space between the two. Depending on how fast the tape is moving, there is a significant delay between the moment the the sound is recorded onto the tape and when you could hear it. Not only that, but if you're trying to play in time with the other channel/s which have already been recorded, you'd need to anticipate this delay and "hit" the beat before you could hear it. What Teac did was enable the record head to also act as a playback head too. So if drums was recorded on channel 1 you could switch channel 1 on the record head to playback and add a guitar track on channel 2 in perfect sync. Of course studios machines had been doing this ever since Les Paul introduced overdubbing decades earlier but this was the first affordable machine that could do this. The home studio was born and Otari and Teac's own Tascam dominated this market right up to today. We can be mighty thankful for this home studio market since lots of the Pro-sumer stereo machines were designed and bought to mix down these multi track recordings. Some of the members here probably own ex- home studio mastering machines.
Another significant tape/tape deck format was mono. If you collect records, I'm sure you have at least a few mono recordings (enough are being currently produced to prompt cartridge builders to introduce mono versions of some of their stereo models). And if your into jazz, lots of Blue Notes (all the 1500 series ) were originally recorded in mono (can you imagine getting your hands on one of those!). There are actually two pretty popular mono formats. One was a full track (full tape width) and 2 track mono (I can't believe that no members jumped on me for forgetting this is the 2 track discussion). The 2 track mono is like a 1/4 track stereo and requires a tape flip to listen to the second side.
There are, of course, lots of other formats such as 24, 16, and 8 channel and some early consumer machines had combination record/playback heads, heads that rotated or raised to have a 3 head 1/4 and 1/2 track playback machine. If anyone has questions regarding these, feel free to ask.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: jgbeam on August 28, 2008, 05:31:18 am
Great stuff, Steve.  Thanks for the time you're putting into this.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: steveidosound on August 28, 2008, 10:38:57 am
Not to devolve too far into head trivia, but there is a class of consumer machine that people may frequently encounter that is NOT compatible with TP tapes. This is the 2 head 1/4 track format where the record and play functions are in one head as you described in "sync" playback using the record head in the last post. In fact some Tascam multitrack (8, 16) use this design too so the signal is always  in sync. It's just harder to optimize record play frequency response and impossible to monitor what you have just recorded on the fly without rewinding with a 2 head (erase, record/playback) system.

As an aside,
yes trivia buffs, that is what the "tape monitor" button is for on many many pieces of audio equipment. It continues to send the program signal to the tape output jacks while allowing you to hear the tape recorder output that can then be switched between tape and input to compare recorded quality.  Some may have forgotten or be too young...

But I digress.

I have also seen auto reverse 2 head designs that play and record both directions. These would have (from left to right) reverse record/play, reverse erase (remember, the tape would be moving the other direction), forward  erase, forward record/play.

And I own a semi pro 2 head design  2 track 15 ips. (inches per second since we are explaining things here) old tube Crown recorder. So at least one 2 track stereo machine is not 3 head !
Title: Re: Heads- Pt.3 Other formats
Post by: steveidosound on August 28, 2008, 11:46:07 am
On one of the Technics machines (which playback in 1/2 and 1/4 track stereo) it depends on which model (1500 or 1506) on which head playback is first and which is last. A 1500 records in 1/2 track stereo and plays back in 1/2 and 1/4 track stereo. Once again the old rule applies. Erase>Record>Playback. If it records in 1/2 track stereo than the 4th head "must" be the 1/2 track playback head. If it's a 1506 which records in 1/4 track stereo, than the 4th head "must" be a 1/4 track playback head.

This feature of the Technics is atypical of multi format decks, in that the 4th head is in the main format of the machine and the opposite format head precedes all the others. As in 1/4 track play then 1/2 track erase, record, play. In most other dual format designs the opposite format additional playback head is after the primary format playback head.
 As in 1. 1/2 track erase, 2.  1/2 half track record, 3. 1/2 half track play, 4. 1/4 track play.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: ironbut on August 28, 2008, 05:21:28 pm
Hey Steve, thanks for those corrections/additions. In the 1/2 track post I was trying to show a Studer 807 picture with the Sony but I guess it was too big a file. It was set up for having the "extra" playback head last just like you said (Duh!).
As I said before, I encourage any and all to post info that I've omitted  or gotten just plain wrong (I'm pretty much doing this off the top of my head). This thread is, after all, to educate and not to mislead (like my other posts). Before I move on to a totally different subject, I'll wait a week so we can keep these in the same general area.
Title: Head Wear
Post by: ironbut on September 01, 2008, 11:42:52 pm
By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-09-01

Ok,.. just a little head basics. I won't go into lots of technical stuff since this is a beginners guide. Heads are (see top illistration) made of laminations of alloys in 2 main parts. If you look at the bottom cross section, there's a right and left half. To orient you, the tape would be traveling left to right or right to left across the top of the bottom picture. You can see that the haves are made up of "C" cores just like some transformers. Between these cores is a small space called the gap (of all things). The gap is the muzzle of the head. It's where the magnetic flux is allowed to flow out of the head and magnetize the tape. There's a spacer placed into the gap and the whole thing is epoxied into a single piece. One thing to keep in mind with these transducers is the extreme tolerances that they are machine and polished to (we're talking micro inches here). And just like lot's of things here on the planet earth, the material that heads are made of are a balancing act of compromises. In this case, it's between permeability and hardness (output and wear characteristics).
You might ask about the "glass" heads that Sony and Akai used in many of their latter models. I owned a couple of those and the problem with those heads is that they don't wear like a metal head which is usually pretty regular and smooth. They develop microscopic shearing of the crystals that surround the gap. After a while these develop into micro-chips (Hey,.. don't go there CV!) and can do real damage to your valuable tapes without you ever knowing it. Once they go bad, they have to be replaced.
With metal heads after they get worn, they can still be resurfaced (lapped). If you look at the first illustration there's a area on the top labeled "Depth of Gap". When a head wears, a flat spot begins to appear where the tape makes contact. An extreme case of this can be seen in the photo on the right. A head can be relapped until the "depth of gap" begins to equal zero. Since the gap spacer is just that, a spacer, when the gap begins to open up like the track on the bottom of the photo. That head is history.
When the wear isn't nearly as extreme as it is in the photo, the head can be reshaped and polished. How fast a head wears depends on several things.
The hardness of the metal the head is made of.
The speed that the machine is used (30 inch per second machines will wear out heads much faster than 7.5 ips machines)
The abrasiveness of the tape that's used.
The tape tension the machine is set at.
The cleanliness of the tape path and tapes.
Proper adjustment of the heads and guides.
Temperature and humidity (heads will rust ).
Most machines you'll come across aren't going to be as obviously worn at the picture above and to get a good idea of the wear you should use a magnifier of some sort and a good light. Look for the shinny flat spot (which all will have to some degree) and the real tell tail clue is grooving. This is something that you can feel. A head that needs relapping will have a ridge that you can feel with your fingernail (be very gentile, remember some of these heads are made of soft metals and you don't want any scratches on them). Even if you feel this ridge, it doesn't mean that the heads that worn either. Many heads have what's called "edge relief slots" cut into the surface right where these ridges would normally be found. They're there to keep the tape edge from being damaged by a ridge and also to prevent shedding oxide from being trapped along these ridges and escalating the tape and head wear. So, unless you get a good look at the head, you may just be feeling these slots. Also, it's important to see if the wear is even or not. That will tell you more about the condition and adjustment the heads and tape path were in during the majority of service. These are all great clues on how well the machine was cared for or if it was taken to a total hack for regular servicing. If you already own the machine, examining the head wear pattern will tell you if you need to take it in for adjustment. Worn heads can result in high frequency loss, excessive tape wear, inconsistent output (dropouts) and loss of overall output. As you can see from the open gap on the bottom of the head in the photo that this machine either needed to have the heads or guides adjusted. If the uneven wear (from top to bottom) was the result of the head being tilted back, the adjustment that would correct this (here it comes!) is called Zenith.
Just a few more things about heads for this post.
If you should need or choose to replace your playback head/s here's the main things you need to know when you choose one. The two spec's usually associated with them is DCR and fluxivity measured in nano Webers per meter (nWb-m). A service manual will have these figures. The fluxivity is a reference number when you wish to choose an alignment tape too. 185 to over 500 nWb-m heads can be found. Aside from those two figures, many times space available will be another determining factor for which heads can be used with a particular machine. Remember that with playback heads they almost always have a shield around them so the fit can be tight.

If you're interested in more info regarding relapping and head wear, John French is the man and his web site is full of info.http://jrfmagnetics.com/

Here's JFR's procedure when relapping heads:

In the JRF alignment procedure each head (erase, record and playback) is
aligned for track placement (referenced to the tape guides and set within
.0005), zenith (90 degree tilt), wrap (gap centered on tape contact scrub
pattern), and azimuth (90 degrees).  Head assemblies that do not have tape
guides attached to the head plate are mounted on our lab fixtures that
simulate the recorder tape path (with guides for height reference).

Upon re-installation of our optically aligned assembly we recommend the
use of a test tape to optimize the azimuth for phase.  This is required
because of the tolerance differences between tape width (typically .246)
and guide width clearance (.252).  As you can see, there is about .006
clearance which can allow the tape to enter the assembly incoming guide
low (or high) and exit the outgoing guide high (or low).  This potential
tape path error along with the quality of the tape slitting
and/or other components in the tape path (such as the pinch roller) will
have an effect in the azimuth that cannot be anticipated in the lab.  We
are generally dead on about 70% of the time however, I always recommend
the use of a test tape.

Title: Magnetic Recording Tape Pt 1
Post by: ironbut on September 06, 2008, 03:11:10 pm
OK, that's enough on heads exclusively. To begin with recording tape, I'm going to send you to the National Media Library for a bit. This is a document that's directed to libraries and other facilities that may be dealing with recording tape in their collection. It includes sections on open reel analog, video, and digital tape. You can pass over the sections dealing with other formats of magnetic tape, but you may also find some interesting things contained in these sections which will broaden your understanding.
Those of us who are old enough will remember the days of large mainframe computers (being here in Silicon Valley I have lots of friends who worked with these at IBM and Control Data Corp). Some of the last major R&D that went into tape transports came from improvements in these data banks.
Bear in mind while reading through this document that some figures given are for a worst case (tape lasting only 10 years for example) and we will later outline what would constitute such a worst case.
There is a glossary and a tape care guide from Ampex but here again, there are items which aren't very relevant to our use (such at reel collars, which were the plastic "bands" that went around the circumference of a reel that kept dust from entering, mostly for computers).
Please pay close attention to discussions of sticky tapes since getting your head around the "stick>slip" mechanism is important. This will be a recurring theme in latter discussions (it's really an extreme cast of very uneven friction).
So here you go,.. "Take it away Dr. Bogart!)
Title: Tape Basics 2
Post by: ironbut on September 13, 2008, 01:36:09 pm
By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-09-13
Once again, I start this episode with some pretty pictures. Nothing is too good for my special friends here at the Tape Project.
The first two are pictures of the different way that light shines through acetate and polyester tape. Holding the reel up to a light will show that the acetate lets light through. This was important since acetate was the backing that was used for films in the early days. This is the easiest way to determine what you've got. The most important reason for identifying an acetate tape is that, as opposed to polyester backed tape, acetate will not stretch. The older the acetate tape is, the more brittle it will become. For that reason, very careful handling needs to be taken to avoid breaks. Some of the things that you should do is to attach long lengths of leader ( I now splice in 2 full turns of white leader tape and 5 full turns of RMGI recording tape that I have around, just like the Tape Project tapes are done). The reason for this is that there is "no" reason that I ever have to subject the acetate to starts and stops or handling at all. The other thing to avoid is rewinding or fast forwarding these tapes. Of course this can be time consuming with 1/2 track stereo tapes but like I said,.. avoid it if you can.
This brings us to an often mentioned term of "gentile tape handling" or tape handling by a machine in general. This encompasses just about every adjustment on a machine and really starts in the design of the tape transport. For now, I'll just mention the basic adjustments that are directly related to the preservation of your tapes.
Brakes- The brakes should slow the two reel as a team rather than fighting each other. If you turn the reels on your machine with it turned off (and the brakes engaged) you'll notice that the turntables have more resistance in one direction than the other. In fact, you'll find that the side that would be pulling the tape (take up reel) always has more braking applied than the side that would be supplying the tape (supply reel) no matter which direction the tape would be traveling in. You can imagine that if the opposite were true than breakage or stretching would occur. So, having the brake tension and the timing of the braking just right is important.
Tape Tension- On most machines, it's the motion of the capstan that controls the flow of tape during play (I'll get more into the what and whys of capstans latter). The reel motors pull the tape in opposite directions applying tension to the tape. You can see this for yourself if you turn your machine on play without a tape threaded on it. The tension helps keep the tape flowing smoothly through the guides and creating an even tape pack as it goes. Correct adjustment of tape tension is important to prevent slippage as the tape is metered through the capstan/roller assembly.
If you look at the third photo of "uneven wind" you will see one of the main causes of problem tapes. Tape pack is how evenly the tape appears from the side and indicates how each layer of tape is laid upon the layer underneath it. Anything that the tape comes in contact with on it's way from the supply reel to the take up reel effects tape pack. That includes air. In fact, one of the main causes of an uneven wind is air. On the sides of a tape reel there are holes of one sort or another. On the Tape Project reels we have cool looking circle/square/triangles. On plastic reels, they're more like the holes that form spokes but it's the holes that are important. These are called windage holes and for good reason. As the tape winds onto the layer beneath it, there is air pressure created between them. Of course there is much less pressure the slower the tape is laying down but the faster this happens, the more likely that the air pressure will begin to act against the tape tension. The windage holes help to release some of this pressure. But this is one of the reasons that a tape has a less even wind in fast forward or rewind.
So what's so important about getting an even wind?  The tension that's applied to the tape as it travels through the machine doesn't go away once the tape is on the reel and put away . It's still there pulling each layer of tape toward the center of the reel. If the tape is stored like the third picture, the edges that are unsupported are allowed to move farther toward the center then the rest of the tape. Even a relatively short time of storage in an uneven wind will give this curling a memory which may not show up except on playback. If you laid a strip of a "curled" tape on a flat surface you'd see that it won't lay flat. The oxide side is lifted off the surface by the curling and the same thing happens when it tries to lie flat against the head. This results in a loss of signal on that channel. And after the discussion of heads told you, if it's a 1/4 track tape, your left channel will be lower in volume or at least, have some high frequency losses.
Other problems associated with an uneven wind is that when a tape is correctly wound, the oxide is protected by the other layers of tape on top of it. When the tape is sticking out on an uneven wind, the oxide on those layers are exposed to dust and impurities in the air.
A correctly wound tape will appear flat and a little shinny through the windage holes. The best way to ensure that this happens and avoid "curling" is to store your tapes in a played condition rather than fast forward or rewind. If you look at the polyester example, it looks pretty good except for a couple of spots that appear as a dark lines. These were probably caused by stopping and restarting the tape at those points. A correctly adjusted machine will minimize these and except for very long storage, I wouldn't worry too much about this.
Probably the most common problem with any tape is called drop outs. These appear as momentary drops of the volume on playback. The most common reason for this is dust or some other contaminant on the oxide surface which interrupts the tape/head contact. This can happen to even the best cared for tape and the narrower the track (1/4 track) the more obvious and distracting it will be. Luckily many times these contaminants can be removed. If you collect a lot of eBay tapes, you should keep a roll of Pelon cleaning tissue around. This can be obtained from US Recording Media and depending on your tape path, it can be held on the tape at any easily accessible spot and will gently clean the oxide side of your tape as it's moving. Since it's usually 7" reels that I have to clean, I use it just after the tape comes off of the supply reel. I use an old aluminum film container that I epoxied a thin suction cup on the bottom (which I kinda smooshed in) so when I stick it to the surface of my deck, it's almost flush. Then I tape some Pelon on it and play it at 15ips. I rotate the can a couple of times to keep clean Pelon on the oxide. (edit: I usually just use my finger on rewind now)
Just one other thing to mention regarding acetate tape in particular, never bake it! You shouldn't have problems with sticky shed (as mentioned by Dr. Bogart) with this type of tape but if you do, baking will ruin acetate so another solution will need to be taken.
Well, I think that's enough for this post. Next time I'll talk a little about other common problems.
Title: Tape Basics 3
Post by: ironbut on September 17, 2008, 11:14:14 pm
Sorry, no pretty pictures to start this one out. There are a number of problems you'll encounter along the road especially if you've decided to collect older tapes from auction sites or elsewhere. One that you'll come across even if your tape collection is still small is called print through.
Print through isn't something that's damaging to the tape itself but rather, it's distracting and interferes with your enjoyment of the music. It manifests itself as a pre or post echo on playback. This is similar to crosstalk that we discussed earlier in our discussion of heads and height adjustment. It's easy to tell the difference between the two since the sound of crosstalk is usually backwards while print though is not (this is on 1/4 track stereo). The sound recorded on the tape is printed on the tape by magnetizing the oxide particles. If a tape is left unplayed for very long periods, these oxide particles will begin to influence the oxide on the tape adjacent to it. A good analogy to this is the way that the early plasma screen TV's, if left with the same picture on it for 10's of hours, would be left with a ghostly image of that picture forever.  Luckily, most print through isn't heard because the music intentionally printed on the tape usually completely obscures it. It's particularly distracting during quiet passages of music when loud sections have been superimposed upon it. There's no known cure for it but there are things that can be done to help to prevent it.
The main thing to do is play your tapes. Even if you had the mythical perfect tape transport, since most tape will stretch, the odds that your tape would be wound exactly the same way twice is pretty much impossible. So do yourself a favor (in more ways than one) and listen to all your Tape Project tapes at least a few times a decade. That may sound funny but there may be some of the releases that just don't float your boat and in a decade, we'll have 100! Woo Hoo, won't that be cool! But of more immediate concern are old tapes you might buy. If you've collected for very long, I'm sure you've bought a few "dogs" with erased sections, bad splices and tons of dropouts. That will lead you to jump at tapes advertised as "still sealed" or "never played" and bid your kids college fund on them. Well, everyone has a personal tolerance level for different audio distortions and I have to admit that mine is pretty high for print through, but if your looking for tapes that don't have it, these unplayed tapes aren't for you. They're more likely to have audible print through than ones that have been played from time to time. You can reduce the level of this print through by repeated playing or rewinding. Some say that it can be reduced by over 2 dB but like I said, if the music is great, I can overlook it.
Stretching The main reason for tape stretching is poor machine adjustment. When you push the play button on a tape deck, several things happen.
1. The brakes release
2. The reel motors engage
3. The pinch roller/s push the tape to contact the capstan
The exact timing and order of these elements will vary from machine to machine but one thing is constant,.. improper adjustment of these will cause tape stretch. In actual fact, proper adjustment will cause tape stretch too but not enough to damage the tape. The thinner the tape backing, the more the tape will stretch so I usually try and avoid buying tapes that have multiple albums on them since that's how they fit them on one reel.
A stretched tape can't be fixed and the "wow" sound that is evidence of this problem is usually accompanied by dropouts since the oxide usually sheds because of the increased length.
Broken tape or bad splices If you buy really old tapes such as the acetate tapes discussed in the previous post, you'll eventually have to deal with a broken tape or fix splices from the previous owner/s which were made to either fix breaks or change song order or some other editing.

By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-09-17
This is a splicing block. To fix breaks, splices or add leader to the beginning or end of a tape you need one of these. As with most of the tools that I'll mention, US Recording Media sells them. You'll also need some splicing tape, single edged razor blades and a roll of leader. I was never taught how to use one of these but the basic use is pretty straightforward and the more you use one, the easier and better the result will be. As you can see, there are two slots that cross the length of the block. The slot on the left (diagonal) is for editing and the one closer to the middle is for general purpose. There's also a channel that runs the length and is made to fit the size tape that you purchased the block for (there are 1/4" to 2" blocks). I'll use the addition of leader as a example.
Place the reel of tape on the left of the block. Place the end of the tape that you want to add leader to in the channel oxide down (no matter why you're using the splicing block, always place the tape oxide down)with around an inch past the middle slot. Press the tape securely into the channel.
Place the reel of leader(or a pre cut length) to the right of the block and place the leader into the channel with and inch past the slot. Press the leader into the channel on top of the tape. Use the razor blade and insert into the slot above the tape/leader and slice it down (think paper cutter) cutting both. Use the corner of the blade as a pick and slide the leader end out of the way without moving the tape or the rest of the leader. Take 3/4" of splicing tape and line it up with the channel (this is the part that takes some practice) by looking straight down at the tape-leader joint. Apply a little pressure to the splicing tape and remove the spliced tape/leader from the block. Put the joint on a hard surface and if you're happy with the splice, apply more pressure to the splicing tape. If there's not splicing tape overlapping the tape/leader and is perfectly straight, congratulations! Measure off the amount of leader you want (I usually add at least 3 full turns) and snip it with a pair of scissors.
If you're fixing a break or a bad (old) splice I use the same slot. The angled one is to make a smoother transition and you can try that one too but the tempo gets interrupted either way but you may prefer the angle. Other than that, there isn't that much difference just remember that the splicing tape is always applied to the back and not the oxide side of the tape.
Mold or mildew This usually appears as a dusty white coating visible on the sides of the tape. For the most part, unless the tape is fairly valuable, it's best to discard it since the spores will contaminate your other tapes via your machine as you play them. The mold is a health hazard to boot.
Just a word or two on the term tails out. With 1/2 track stereo tapes (like the Tape Project tapes) which are unidirectional, it is considered best practice to store the in a tails out configuration. This means that the tape must be rewound to listen to it. To do this you place an empty tape on the left reel platter and the full tape on the right. Thread the tape as the machine is normally done and rewind it fully. Now the tape is heads out and the full tape is on the left side (supply side). Now it will play correctly. One thing to keep in mind with 1/2 track stereo tapes is that no matter how you manipulate the reels, flipping it or moving it from side to side, rewind, play or fast forward, as long as you thread the tape the correct way, it will only play either correctly or in reverse. Nothing you can do will move the left channel to the right. That said, if you wish to change a heads out tape to a tails out one and you don't care what reel it's on, all you have to do is put the heads out tape on the left reel platter and put the reel you're going to keep it on, on the right. Play tape and now it's tails out. If you want to keep it on the original reel, you'll need a second empty reel and put it in place of the now empty original reel and rewind the tape onto that one. Now replace the empty reel on the right with the original reel and play the tape onto the original.
Tape care tips.
Title: Tape Basics 4
Post by: ironbut on September 24, 2008, 10:40:23 pm
This installment will be devoted to tape care. For most members who have record collections, some of the day to day precautions of vinyl handling will hold them in good stead when it comes to tapes. Direct handling of the oxide side should be avoided since the oils on your skin can attract dust and dirt and with some formulations, it can lead to shedding (the oils tend to be acidic). And leaving a tape on your machine and not in the proper box can lead to dust collection on the oxide side the next time it's played.
You may have noticed in the posts dealing with audible tape problems, almost all of them result in poor tape to head contact. This isn't a coincidence as magnetic fields decrease drastically with distance. You've found this out yourself if you've ever tried to put too thick a note on your fridge with a pizza magnet.  It's not just the extra weight that keeps it from holding, it's the increased distance for the most part. So when you hear a drop out, it's usually pretty broad band and much greater than the size of the dust particle would seem to warrant. Unlike a record needle which is forced to move by the dust itself, a drop out is that dust particle holding a portion on the tape (sometimes the entire track) far enough away from the head to make it sound like a momentary loss of signal (it's actually there but significantly reduced). So if your a vinyl lover, transfer those good habits over to your tape handling. If you're not, develop some. It won't take long before you don't have to think about what you're doing.
For much of this posting, I've pasted the "Tape Care Tips" page from US Recording Media;

    * Keep it clean: Playing tapes is a pleasurable experience. Your tape deck's heads, guides, and pinch roller(s) are on the front line of gently handling your valuable tapes. One thing that can mess up the gentility of  this process is dirt. There's a degree of static built up, especially in desert climates, on the deck as well as your tapes. The tape heads and guides must be kept clean, not only for sonic reasons but to protect the tapes you're playing. We've seen many cases where dirty heads and guides have scored (scraped) lines along the length of the tape, and especially the edges. It's important to keep these surfaces clean, for a tiny piece of oxide or other dirt stuck to the heads or guides can do quite a bit of irreversible damage to your precious tapes no matter how new or old they are. In particular, keep in mind the edges of the tape guides where the edges of the tape live must be kept clean. Many people use unwaxed dental floss to clean these tiny corners. If the edges of your tape are getting worn, you could have nasty tracking problems, because it's actually the edges of the tape that guide it through the tape path. And if these edges get wavy or scored, you could have some major problems. Se strongly suggest using our CL-100 head and guide cleaner to clean up these surfaces and our RC-5 for cleaning the pinch roller when needed. Oh, and No Smoking.
    * Check the condition of your guides and heads: Tape guide parts like lifters are supposed to be round, not showing a worn, flat spot. If there's a flat spot worn on any of your tape guides where there's clearly an edge that can be grabbed by your finger nail, they should either be repaired or replaced because the edges of these flat spots are very hard on tapes and can damage them beyond repair, especially in rewind or fast forward play. In some cases the guides can be turned in position revealing a new surface. Sometimes they can be sleeved with a stainless steel outer casing, and sometimes they have to be replaced. Some decks like a Revox A77 have rotating guides which is a good idea. Some decks like a Nagra have extremely hard surfaces, ruby in this case, and they are very resistant to wear, although extremely expensive.  Some decks have very hard stainless steel guides, but others have very soft metal, even brass which can wear more readily.
    * Demagnetize your Tape Path: Tape heads and guides tend to pick up magnetism from the tapes you're playing and rewinding over time. This magnetism can slowly erase the high frequencies on your tapes as well as create additional noise on playback/record. The magnetic fields can actually get strong enough to make proper calibration of your deck very difficult and make what should be quiet recording quite hissy. A good head demagnetizer like the RB Annis Han D Mag used on the entire tape path will eliminate these magnetic fields. It takes a fairly powerful demagnetizer like the Han D Mag to thoroughly erase these parts, as the small pencil type units simply aren't strong enough to demagnetize steel parts.
    * Make Sure Your Guides/Reel Platters are Aligned Properly: The tape guides, as opposed to the tape lifters which lift the tape away from the heads for wind functions, are the one thing on the deck that determines where on the tape heads the tape is going to travel. We've had so many cases where these guides are forcing the tape vertically into position because the reel platters are set too high or low on the tape deck. You might even see tape shedding at the left hand guide's edges. With very thin tape you might be able to see a distortion on one of the tape edges as the tape approaches   this first guide.  After playing through a tape, there should be equal distance from the top of the tape pack to the inside of the flanges on BOTH sides of the reel. This will show that the right side, or takeup, tape platter is at the proper height with relation to the tape guides and heads. If you rewind a tape, the same thing should happen on the left, or supply side, of the deck. Ideally after playing through a tape and flipping it over to the supply side to play the other side of the tape (assuming a 1/4 track recording) the tape should leave the reel in exactly the proper position to be lined up with the left hand guide without relying on this guide to force the tape into proper vertical position.
    * Just In Case: You may want to consider using a UPS, or uninterruptable power supply, on your open reel deck. Why? If you're rewinding a tape to play it and the power goes off, even briefly, it can be a mess. You can possible ruin your tapes depending on the transport.
    * Storing Temps and Humdity: All tapes, even video, should be stored vertically and in a dry, cool environment. Ideally for storage, keep them between 65 degrees to 69 degrees and a relative humidity of 30% to 45%. For very long term archiving, store your tapes ideally at around 50 degrees with a relative humidity of 20% to 30%. One big thing here is temperature and humidity swing which is very hard on recorded media. Humidity or temperature should not swing by more than 10% over a 24 hour period.
    * Never store your tapes horizontally: Always store your tapes in the played condition vertically. In other words, don't rewind your tapes and store them that way. You want to make sure the layers of tape sit directly atop of one another with no edges sticking out of the tape pack. These exposed edges are not only subject to damage but might even begin to get wavy due to the stresses applied to the tapes when used. This is especially critical when using thinner tapes like 1 mil or less.
    * Keep Away From Magnets: Do not lean your tapes against the side of electronics, especially of all things, loudspeakers. Keep away from transformers like those found in flourescent fixtures for high intensity halogen lights.
    * Erasing tapes: To save on unnecessary wear on your deck and to obtain the quietest erased tape possible, always use a good, high powered bulk tape eraser like the Verity VS250 or a tabletop model. You can't get as quiet an erase using the deck to begin with, so why subject the deck to unnecessary and costly wear?
Courtesy of http://usrecordingmedia-store.stores.yahoo.net/

How to tell something is wrong
Of course, when the sound seems distorted, muffled or just off is going to be the first clue. This could be the result of any of the adjustments on the machine, worn heads or downstream of the tape machine. If you have a headphone output or a dedicated headphone amp you can really eliminate some things quickly. I do all my adjustments with headphones since it makes changes in sound much more obvious.
Another thing to be on the lookout for is oxide shedding. You shouldn't be able to see oxide on the capstan, guides or heads after playing one tape. But if something is awry in the tape path (guides, reel tables, tension, pinch roller slipping, braking) the tape could be scrubbing or scrapping and releasing oxide. If you suspect one of these problems, make sure things are very quiet and listen to the tape as it makes it's way from one reel to the other. You should use a tape designated for adjustments, not one of your valuable Tape Project tapes. With your ear close to the machine playing the tape, use your finger and push the edge of the tape against the side of one of the guides so you will learn what it sounds like when it's scrapping. Then play the entire tape since some of these problems only appear when the tension is at a particular point.
Flanging This problem is related to the paragraph above. The reels themselves can become warped or bent and no machine adjustments will counteract this. Flanging is the rubbing of the tape against the "flange" of the reel usually on one spot on the reel. This will result in poor tape packs and can cause oxide loss in extreme cases. Be careful buying those cool looking aluminum reels off of auction sites unless they're too cheap to pass up. I've tried to straighten bent aluminum reels and never did anything but make them worse. There may be a way to do it but I'd rather just buy a couple new. It's a good idea to have two in case one gets bent or you want to change a 1/2 track tape from heads out to tails out.
Uneven wind This can vary from tape stocks or reel types. Unfortunately, there aren't any machines that will adjust themselves other than constant tension (some Studers). And some reels will not allow a nice smooth tape pack no matter what you do. So if you find one or two tapes with an uneven wind but the others are fine, try putting it on another reel before making adjustments. Some tapes with quality control problems (they do happen from even to the best manufacturers) may have been slitted (cut down from a wide roll of tape down to 1,2,1/2 and 1/4 inch) incorrectly and will rub and shed like crazy. The only cure for this is to return it.
High Frequency loss Boy, this is the catch all for tape problems. Almost every misalignment , worn part, and tape problem will have loss of high end sparkle.
All and any problem with reel to reel tape/machines should always be answered by first doing a thorough cleaning and then trying to repeat the problem. Many seemingly non related problems can be solved this way. It's easy and quick so why not?
So that ends the tape section of this primer and next we'll get into cleaning and regular servicing and a list of stuff you need.

Tape Timing Chart (Nominal minutes)
Reel       Tape                 Footage         Speed [in/s (formerly i.p.s.)]
                      1.875  3.75   7.515   30   
5-inch1.5 mil6006030157.53.75
1.0 mil900904522.5115.5
0.5 mil Double   12001206030157.5
0.5 mil Triple1800180904522.511
7-inch1.5 mil12001206030157.5
1.0 mil1800180904522.511
0.5 mil Double   2400240120603015
0.5 mil Triple3600360180904522.5
10.5-inch 1.5 mil2500240120603015
1.0 mil3600360180904522.5
0.5 mil Double   48004802401206030
0.5 mil Triple72007203601809045

Title: Basic Machine Maintenance
Post by: ironbut on September 29, 2008, 11:54:39 pm
Well we're finally at the point that we can start putting things together into something that works "in the service of music".
As the Tape Care posting indicates, keeping your tape heads and guides sparkling clean is hugely important. For this you'll need a cleaning solution and an applicator. If this is your first tape machine (open reel or cassette) you're probably in luck since for basic cleaning 90-99% isopropyl alcohol and Q tips will do fine. Of course it can't be just any alcohol or Q tips (don't use plastic handled ones since the plastic can scratch the head surface). Alcohol that's not labeled, as these higher concentrations are, contain lots of water. The problem with using water on your tape path is that even though a great deal of effort has gone into making the oxide surface of the tape as slick as possible, it's still slightly abrasive (as evidenced by head wear and flat spots of fixed guides). This freshly polished metal is the most vulnerable state for rusting. If you take a piece of steel and sand it's surface it will begin to show signs of rust in less than an hour. This kind of light cleaning should be done every ten tapes or so depending on the tapes that you've been playing. Most old tapes will shed loose oxide much more especially on their first couple of plays. So it's important to examine your tape path for oxide build up. On my machine it only takes a glance at the erase head to determine the amount of build up but you'll learn pretty quickly as you look at the amount of crap that collects on the Q tip. Every four or five times you clean the tape path, it's a good idea to use something a little stronger. I use the Lasermedia CL-100 US Recording Media sells (and mentioned above). Doc uses Naptha and there are other head specific cleaners too. One nice thing with these solvents is that you can use them to clean dried up grease if you're restoring the machine too (which takes a while with alcohol). With these solvents, after you clean a head or guide, it's a good idea to wipe it with the dry end of the Q tip to remove any excess. Allow these to air dry for at least 15 minutes before threading a tape since they'll destroy the binder of the tape (which is what they're supposed to do).

WarningBe aware that all "tape head cleaning solutions" aren't created equal. I use the CL-100 because it is recommended by US Recording Media but past that, I can't say that I know that it's the best thing for my heads or if it might be completely wrong for another type of head.
In any case, I recommend that you use it just for tough jobs and wipe any excess off when the cleaning is done.
Alcohol is what I use 99% of the time and only when that won't clean stubborn bits do I resort to CL-100.

By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-08-25 photo courtesy of Richard Hess http://www.richardhess.com/tape/index.htm
Here's our old friend the Sony APR head assembly. If I was cleaning this with alcohol, CL-100 or naptha, the procedure is the same.
I keep these solvents in a cabinet in the bathroom just in case I spill it. I'm not really worried about the carpet or floor but these chemicals are very nasty (contain carcinogens) so if I spill it in the bathroom it can be cleaned and closed off till the fumes dissipate. It's also where the Q tips are.
You don't want to soak the Q tip or if you do, roll it on some tissue so it's just wet (I roll it on the toilet roll for a surprise for those special house guests).
With a strong light directed on the assembly, I'd start with the leftmost guide and clean the center all the way around if possible then direct the tip on the guide edges. The tape edges go all the way into these corners. So should you. Don't forget to wipe it with the dry end of the Q tip.
The heads on the left of the idler would be next and if the Q tip isn't dirty enough to transfer what's on it to the heads, you should be able to clean the timecode, erase and record heads. Clean all heads in the directions of tape travel. As you'll recall, heads are made of laminates stacked vertically so they have the equivalent of a grain that goes horizontally. All features of a head (relief slots, tracks) are also horizontally oriented and if  you were to scratch the head, (and you may not even be able to see this) it is less likely to cause an audible problem.
Go back to the bathroom and wet the another Q tip and clean the idler as you turn it. Be careful with any rolling guide like this since the solvent will clean the oil right out of the bearings and onto the surface that you're trying to clean so nicely. Clean the playback head and finally the last guide just like you did the first one. Well, not quite finally, that's just the head assembly. Your machine will have other tensioners, rollers or guides that are separate from the heads. The same procedure is to be followed. Just remember that if it's a roller, there's a bearing in there and if you don't want to have to pull it and re-lube it, keep the solvents out of the insides.  Discard used solvent supplies outside in the trash so no one has to breath the fumes except the flies.
So, what about the lifters and the tape sensor?
The lifters on this machine are ceramic and can be stained by solvents mixed with oxide (what do you think they make brown wood stain from?). Yours are probably metal so they would be cleaned in the above paragraph.  So that brings us to another esoteric cleaner. Formula 409. Anyone who remembers the Fantastic vs. Formula 409 wars of the 70's will have a favorite of these two and be equally sure that the other one's crap! For those who are too young to remember the blood stained household cleaners aisles of your local supermarket its just a water based all purpose cleaner. Squirt a bit on a Q tip and wipe clean all easily reached sides of the ceramic lifters and the optical sensors on the tape sensor.
If you're working on this machine or just new to it, clean the areas surrounding the heads and guides so you can tell if there is something that's making oxide shed. Every little clue helps. 409, plain water or even a dry Q tip will do depending on how dirty it is.
While you have the 409 out, wet a fresh Q tip and clean the surfaces of the pinch rollers. You just need to clean these most of the time but just like the heads, it's a good idea to use a rubber treatment a few times a year. I use some stuff from MG Chemicals called rubber restore but I already had a lifetime supply of this.
Here's a very important item to use before you think that you're done cleaning the head assembly. It's a magnifier of some type. I have a 10X lens from Swift that's small, cheap and clear. Get used to using one after those solvent cleanings and don't forget to check those corners ,.." I think I saw a potato growing in there!"  Seriously, it's very easy to get a glob of adhesive from a splice you didn't even know was there (I guess if it's oozing glue you'd be able to hear it though) or a drop of the champagne you and your spouse popped open when the last of your kids moved out.

Note The above discussion of pinch rollers (and some idlers and capstan surfaces) pertains to ones which are surfaced with rubber compounds. Urethane rollers/parts are becoming more common and they are not to be treated with chemicals meant to be used on rubber. I understand that water is recommended but it would be a good idea to ask the manufacturers if you have a particular problem that water isn't working on.

So what about demagnetizing? All these metal parts will become magnetized by the imprinted tape. It is very slight so demagnetizing just needs to be done a few times a year. It does require a strong demagnetizer and I recommend the RB Annis one that US Recording Media sells. They used to have a kit with a little meter that measured flux but I really think that if you use it with each coming season (four times a year) you'll be in good shape. Follow the included directions and turn off your machine before you begin. You can overload the outputs, destroy the movements in your VU meters and god knows what else (I've done it and it's loud!).

Next a shopping list

Title: Shopping List
Post by: ironbut on October 02, 2008, 01:11:41 am
This list is directed to all Tape Project subscribers. The sheet that's included with each release should tell the story; " Please make certain that your playback deck is in equally good condition before you play this tape.". The preceding post regarding the care and feeding of your tape machine should be followed religiously. Every one of these tapes are the results of a labor of love and are instant collectors items. I believe that they will be recognized as the highest standard of recorded media for the foreseeable future. Due to the limited numbers that these tapes will be produced in, each of them should be preserved for future generations of audiophiles. Of course these are yours to do with as you see fit, but if you choose to neglect them, expect a visit from a mylar clad intruder stepping out of his Hitachi Transport Module with the Temporal Foldback option holding a TP tape with your issue number on it!
So here's the basic list

1. Isopropyl Alcohol 90-99%
2.Q-Tips with wooden or paper sticks (not plastic)
3. Demagnetizer  (RB  Annis)
4. General purpose cleaner (409/Fantastic)
5. Head cleaner (the nasty stuff like naptha or LaserMedia CL-100)
6. Rubber preservative/restorer (several available but different so follow directions)
7. A strong light with a goose neck or easily directed. A bright little flashlight also helps.
8. A magnifier of some sort with a plastic frame (just in case you bump it on the heads)
9. Inspection mirror for examining heads/guides (try and find a small round ones with a penlight attached)

This list is for those of you who wish to do at least some of your machine servicing yourself.

1. Service Manual This is huge. Every machine is different in it's measurements and adjustments. Basic adjustments are usually the same from model year to model year but a service manual will often include pages that list any changes. If things don't look like the pictures or description, don't assume that they're the same. Studio machines in particular can have radically different components and even total redesign of entire areas. Previous owners may have done retrofits or upgrades which may have been ill advised or poorly implemented.
Anytime that things don't seem right, ask in one of the forums and even if none of us have first hand knowledge of it, we should be able to direct to somewhere or someone who does.
2. New non-magnetic tools. There are lots of things that you can do with basic tools. Screwdrivers, open end wrenches, sledgehammer (just joking), needlenose pliers. Don't use the ones that you pulled the tranny out of that panel truck with. Go to the hardware store and buy a new phillips screwdriver with a #2 tip. The parts for these machines are tough to find if not impossible. And even though pretty much all of us will have to do the "shake the chassis" dance a least once when a screw slips into the depths of your machine, patience will recover it with more certainty than a magnetic screwdriver. BTW, this is a dance best done with a partner, these things aren't light!
3.Tentelometer. A what?? This is a meter that will measure tape tension. Actually, this will be one of your most used tool when you do adjustments. The tape transport and head assembly is a system. Almost every adjustment you make to the transport effects tape tension so you'll use a tension meter with these adjustments. These are available for a fraction of their original cost off eBay. You have to have a service manual to know which of the many models that you need. The models and their ranges are listed in the price list on this link. There's also a pdf of the manual here;http://www.tentel.com/prod01a.htm (this is an early example of websites and very clunky to navigate so when you find what you need, save it!)
4. Scale for measuring braking and pinch roller pressure. There are a number of different types from the cheap plastic spring scales available from Edmund Scientific to nice German or Swiss made ones off of eBay. You may need 2 different ones depending on the machines specs but these measurements usually have a quite a bit of wiggle room so it it doesn't require the very best scale. Once again, you won't know which one to buy (weight range) unless you have a service manual.
5. Expendable reels of tape. This is one instance where I can heartily recommend purchasing blank tapes off of eBay. Buy a 10.5" and a 7" reel of tape to use exclusively for doing adjustments. Doing these requires relatively rough handling of tape and a Tape Project tape should only be used as a final test. I have one for brake testing and another for general adjustments. The brake testing one actually has a knot tied into it's end (to slip over the scale) and it's one of my early (and worst) prerecorded tape purchases.
6. Lubricants. There are many opinions on oils to use and depending on where it is used will determine the weight of the lubricant (oil or grease) For the most part, machines with parts that slide against each other should use a grease (I have some white grease called Phono Lube) and fast spinning bearings should have a light oil applied. I use an oil called Zoom Spout Turbine Oil that's available from many Ace Hardware stores. It was recommended on the Ampex list and so far I haven't got a problem with it. You should check your service manual to see what they recommend first. In many cases, whatever they suggest is no longer available.
7. Thick piece of high density foam for laying the machine on it's face. I got some 3 inch packing foam ( the white stuff) and made cut outs for levers, the head assembly, reel hold downs and tensioners so I can lay my machine face down without messing anything up (like all those adjustments you took days to perform).
8. Blue Painters tape, 1.5" wide. This is a low tack tape that really comes in handy. I use it to tape the foam (#7) to the machine, mask the paint on the faceplate when I use the tension meter (you'll find out when you use one that when you hit play, the tape will try and jerk the tension meter and the best way to use it will cause the pointed tape guides to hit the machine.
Of course there are any number of things you'll need like hex wrenches or test equipment but they're machine and/or job specific.

List for old prerecorded tape collectors
This list are things that you'll find helpful to maximize your enjoyment of these older tapes.
1. Pelon. This is a tape cleaning cloth that comes in 2" width on a roll. It's your basic cleaning material and contains traces of the lubricant that dries out over time. Great for minimizing drop outs. For tapes with just a few scattered drop outs, I just cut off a couple of inches and hold it against the oxide side on rewind (if there's any chance that the tape is brittle or otherwise delicate, try the film canister device I outlined in the tape problems post under drop outs.
2. Empty reels and boxes. If you collect old tapes for any time at all, you'll end up with some with useless boxes and/or wasted reels (bent, broken or just nasty). I think that everyone should have at least 2 empty 10.5" aluminum reels for transferring tape. Doc says that the low torque (large hubs) 7" plastic reels aren't being made anymore so if you see some anywhere, post it, but I do keep at least five 7" reels around and at least 5 empty boxes too.
3. Splicing block/tape/leader. I'm a big advocate of the liberal use of leader at the beginning and end of tapes. It avoids so many potential problems that it just makes sense. Make sure and get some single edge razor blades too.

Almost all of the items on these shopping lists can be had from US Recording Media. The others can be had from the drug store and hardware store.
The splicing blocks aren't available from USRM but ATR Services has used ones for $25 (new ones are $69). There are also some ones I found by Googling splicing block for around $40 but you should go for a well machined block if you can. It'll last a lifetime (I've had mine for about 36 years).   info@atrservice.com
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: xcortes on October 02, 2008, 12:36:05 pm
I finally took the time to read this thread carefully.

Fantastic job Steve!

Only problem is that you're scaring me. Every sentence I read I lean more towards sending my deck to Doc to make sure it's in good shape and towards building a hermetically sealed, climate and humidity conditioned dust free room for my deck and tapes.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: ironbut on October 02, 2008, 07:02:30 pm
Hey Xavier, I'm glad you like it and thanks for the feedback. I have to admit that I haven't gone back and re-read any of the postings yet. I probably should to get a feel for the direction this "stream of consciousness" is heading.
I don't mean to scare you guys but I'm afraid that the odds are that a few of the subscribers to the Tape Project will unwittingly, ruin some of their tapes. I may have gone a little overboard on the warnings about all the little things that can damage a tape but since this is a beginners guide, I'd feel responsible if I was to leave something out and the result would be a wasted tape.
On the other hand, I've tried to take the reality of real world use into account in which members who read this will know what should be done even though it's not practical at all times to do this. For an example, I know that I should always store my tapes vertically but my shelving purchases are way behind my tape purchases. As a result, I've got close to 200 tapes stacked everywhere. What's even worse is that I'm working on a deal to buy a lot of up to 200 more! (Yikes! I haven't gotten around to listening to over a hundred that I already have.)
So, you get the idea. I think that developing good habits (just like with records) is the main focus of this thread. This does include;
1. A very careful and thorough examination of your machine every year or so. 
2. Keeping an eye out for tell tale signs of maladjustment (excessive oxide shedding, high frequency loss and the sound of the tape edges scraping the guides or reels).
3. Keeping your tape path clean.
4. Putting your tapes back in their box after listening to them.
Following these four items will keep lots of problems at bay. But you know me, why list four little tips when I can write the Encyclopedia Britannica!
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: Ben on October 03, 2008, 08:37:44 pm
One question here.   Tape hiss: Is it the tape,machine or snake in the other room.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: ironbut on October 04, 2008, 12:43:38 am
Hi Ben, it must be starting to get cold up there by now ( I lived in upper state New York so I know what real cold is)?
The tape hiss is really the noise floor of the tape itself. It's caused by the particles of oxide ( the smaller the better) and the machines ability to take advantage of the dynamic range of the tape. When I first started fooling around with magnetic tape, the signal to noise ratio was one of the main specs that folks looked for when picking a machine. The s/n ratio given was usually with a specific tape. Of course those specs were given for record and play. Todays tapes all have a very large dynamic range so there's more tape hiss from the master tape than from the RMGI 468 that our tapes are recorded on. A couple of the demos of the TP tapes that I've done have had a few guys that had reel to reel machines back in the 70's. They all commented on the lack of tape hiss on these demo tape I used. I have quite a few pre recorded tapes from the 60'-80's and the ones without any noise reduction have quite a bit of hiss. The older the tape, the more hiss they have. On the other hand, these early releases were meant to be the highest fidelity available at the time and most of them have excellent sound. I'm always happy to open a tape box and find that it's an acetate tape even though they tend to be very fragile and extra care is needed in handling them.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: Ben on October 04, 2008, 10:55:16 am
It is roasting here. I am face the sun here, and we are having the last hot days
of indian summer. So with tape hiss, I guess I just live with it. In wonder if it was
more of a problem in the 60's with tube amps, or today with the newer tube,speakers
that are coming out.
PS:I just remembered, I think I like it better than the hidden white noise added to CD's.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: steveidosound on October 06, 2008, 10:32:59 am
After my recent bad experience with whatever is affecting my Moody Blues quad Seventh Sojourn tape, it occurs to me that there should be a section here dealing more with the physical properties of tape as well as the machines. I still would like to know what you do about oxide shed, the infamous tape squeal which you have somewhat covered under tape and head lubrication elswhere, if sticky-shed affects any prerecorded or non back coated tapes, and an explanation of how to bake/dehydrate, when they shifted from acetate to polyester for prerecorded tapes etc., etc.
Other beginners and old timers might appreciate this as part of this section too.
Title: Tape Squeal and Baking
Post by: ironbut on October 10, 2008, 07:29:39 pm
I can see that there is demand for some info regarding Sticky Shed Syndrome and cures for this malady. For those who haven't had the dubious pleasure of owning a tape with SSS, it's main symptom is squealing. This can be very loud and can be easily heard through your speakers as well as from the machine itself. The second symptom is the slowing and even stopping of your machine.
SSS is caused by binder breakdown. As illustrated in Dr. Bogart's link, the binder is the "glue" that holds the oxide to the backing. In the 70's, Ampex changed their binder to a new compound which had short molecular chains. Several other companies such as 3m/Scotch followed suit. Unfortunately, these compounds were latter found to become unstable after long exposure to high humidity. These compounds absorbed the water particles and the binders broke down and appear as a dark tar like substance. What is especially unfortunate is the fact that this new binder was used in their mastering grade products. Some consumer products such as Shamrock audio tape was actually "B" stock of these high end tapes. Ampex accepted blame for the problem and set about finding a cure. Tape Baking was found to temporarily fix SSS.
Here's a chart of the most likely tapes to have this and similar problems;

Manufacturer   Tape Type   Years Affected   Information Source

Agfa   PEM 468   pre-1990?   Goran Finnberg
PEM 469   pre-1990?   Cary B. Cornett
type 1 (cassette duplicator)   ?   Ben Torre
Ampex/Quantegy   406   1970s-mid-1980s (and later?)   Many
Audiotape   See Capitol Q15
Capitol   Q15 (an Audiotape formulation)   early 1980s   Howard Sanner
Quantegy   see Ampex/Quantegy
Scotch/3M   226   All   William F. Lund

This was found at the home page of the Ampex list. http://recordist.com/

The problem became most apparent when record companies began to pull out old master tapes to produce CD's . You can imagine the turmoil it must've caused when they began reissuing properties that they already owned and mining the goldmine that they knew that they had.
Ampex's Cure Like I said, Ampex realized that these short chained compounds were a terrible mistake and changed their binders back to medium length molecular chains (long chain binders were too gooey). They also came up with the notion of tape baking. Agfa's binders had a similar problem and an elaborate microwave system is recommended for their tapes. Their binder breakdown appears differently also.
There are several good sites for instructions on tape baking which I'll list. One very important fact that you should keep in mind with tape baking (which I hinted at earlier) is that it is a temporary fix. The idea is to prepare the tape for transfer to, currently, high resolution digital. A friend of mine has lots of one of a kind, multitrack tapes on Ampex 456 and after he bakes them, they sound exactly as they should but only for a few days to a week. There are other cures such as TP member Marie's alcohol drip treatment Studers and cold playing (could that be where they got the name from?) of tapes. There have been a few claims of permanent fixes but I've yet to see any evidence that it can be done (especially at a reasonable cost).
I've been a bit reluctant to post anything regarding tape baking because for the most part, I've found the problem to be pretty rare with the tapes I've collected. Out of the few hundred prerecorded tapes that I have, I haven't got a single tape with true SSS. I only have a couple of master tapes and several of them, I've never played so there could be a few hiding in there. But unless you have a number of tapes with this problem, and they're unique in some way, I don't think it's worth the effort just to listen to them a few times.
Of course there's nothing wrong with doing a little experimenting if you have a mind to. If so, here's a good link to using a dehydrator to bake your tapes;
BTW It's recommended that you get an accurate thermometer to use with any tape baking.
Title: Oxide shedding
Post by: ironbut on October 19, 2008, 02:27:18 pm
To answer Steve's questions regarding oxide shed, just about any problems with a tape or machine adjustments can result in oxide shedding.
Older tapes are problematic in that they are subject to any misuse by the previous owner/s. Even when a tape seems to be fine on the first couple of plays, it can start to exhibit shedding in subsequent plays. The reason for this is that is usually because of poor long term storage. The oxide could be somewhat loose and the action of moving across the heads and guides can create enough friction/heat to release it from the backing even further. Sometimes the oxide loss will stabilize after a few more plays the same way that many old tapes will shed on the very first play. The only thing that I've found that helps oxide shedding is the use of a tape lubricant like the Last tape treatment. It reduces the friction and seems to stabilize the oxides adhesion to the binder/backing. I use it on almost all of my old tapes and have almost no shedding with them now. That reduces the frequency that I have to clean the tape path (although I do quickly check it after almost every tape). As far as I'm concerned, the only problem with Last's products (I use the head treatment all the time too) is the cost.
If you begin to notice oxide shedding on newer tapes (such as your TP tapes) it's probably a problem with your machine. Things will get out of adjustment no matter which deck it is or how well you take care of it. Heads and fixed guides wear and the grooves that the tape will eventually wear in them will scrub the edges of the tape and release oxide. Improper tension on pinch rollers (too high or too low) will either stretch the tape as the rubber deforms against the capstan from high tension or the tape scrubs against the capstan as it slips from low tension. Slippage can be heard as a veiling (smearing) of the sound. You should use the roller tension recommended in your service manual but I always do final adjustments of it by ear.
In summary, anything that stretches the tape or causes excessive friction can cause your machine to increase oxide shed. Tape formulations vary in the longevity of the binders no matter what the storage conditions are. With the exception of sticky shed syndrome, binders ability to securely hold onto those tiny bits of oxide for 30+ years as we rub it against metal parts (in stock form my Technics has 15 different surfaces that the tape comes in contact in play) is pretty good. Even the worst ain't that shabby.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: astrotoy on October 20, 2008, 09:56:50 am
Steve, this is really great stuff that you are posting. Although I've had R@R machines for over 40 years, I've never understood the details of how they work and how to maintain them. Thanks for all the fine work.  Larry
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: ironbut on October 21, 2008, 09:46:06 am
Thanks for your words of encouragement Larry. Writing this "guide" has given me the opportunity to pull all those little factoids about tape, that I carry around in my head, into something that makes sense as a whole. It's also forced me to go out and check my facts. I've even gotten a couple of books on the subject! (I've only flipped through them so far but sadly, none of them could be called excellent or even that good so far) Thank god for the internet and excellent web sites like Jay McKnight's and Richard Hess'.
I have relied on personal experience to help fill in some of the gaps so some of these suppositions are on shaky ground. Once again I ask that experienced users review what I've written and PM me with items that need to be corrected. Even if something just doesn't seem quite right or I left out something important on the subject, either post it ( I can add a footnote and refer to your post in the original) or PM me and I'll edit the original post. I've tried to leave my ego at the door since this is an instructional guide so accurate info is essential!
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: Ben on October 21, 2008, 12:03:14 pm
Umm Still waiting for the 'How to thread tape on the reel' faq.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: ironbut on November 01, 2008, 11:36:18 am
Hey Ben, if I understand your question, I generally just use the friction of the layers to hold the tape onto the empty reel. That is, I never use adhesive tape to get the tape started. On large reels, I grab the loose end about 4 inches from the end and thread it through to the empty reel pulling out slack as needed. I lay the tape across the hub of the empty reel with a windage hole on top and put a finger on the tape through it. With my other hand I turn the full reel till the 4 inches of slack is under my finger with maybe a half inch to spare. If you don't pull in the slack that little bit can stick out and go tick-tick-tick against the machine which I find real annoying. Now comes the tricky part, I switch hands, securing the tape end (that half inch) with a finger and begin turning the reel. Just as the tape is about to put a layer over the end and my finger, I reach a finger from the other hand through the top-most windage hole and secure the tape just before the tape covers my other finger below and I pull it out of the way. This keeps the beginning of the pack nice and tight. With a little practice it only takes one manual turn to secure the end and you can let the machine take it from there.
Small reels don't take as much slack to get things threaded but, if the brake tensioning on your machine is high like mine is, once the tape is secured on the empty reel, I give the full reel a little help(manually pull out enough for a layer or two) as I wind the first layer over the end. The reason for this is that the brake torque is constant but the smaller reels have a much smaller hub. This results in high tension at the beginning, enough to stretch your tape. This is a huge reason for having plenty of leader on your 7" reels.
Some small reels have no windage holes. They either have a little slotted hole in the hub or nothing at all! With the slotted hole you have to pull an inch or two of slack through it and hold this slack against the reel with a finger as you turn the reel. After the end is totally secured, you stuff the slack into the hole. The ones that they expect you to use splicing tape to secure, I replace the reel. Once you've collected for a bit, you're bound to have a dog or two. If you're going to toss it, save the reel. This is a great place to use those.
Stuff like this can really make you feel like you're all thumbs at first, but after a while it becomes second nature.
Hope this helps.
Title: NAB vs IEC tape eq
Post by: ironbut on November 01, 2008, 11:16:07 pm
Boy, was this ever a hot button topic at the beginning of the Tape Project. This is going to be just a basic overview of the subject since this is still a beginners guide.  Those of you who have phono systems will be familiar with RIAA eq which is used on modern vinyl. This is similar in that it is a pre emphasis and de emphasis system. Just like RIAA eq, this system is used to compensate for idiosyncrasies of the medium.  It would be a happy coincidence if the head/tape interface produced an extended flat frequency response with an inaudible noise floor and realistic dynamics without any help, but that just isn't the way things are. So when they record music onto a tape, one of the things that happens to the music is it is equalized. The inverse of this is done on playback to return it to it's original state. Bear in mind that this is done to the music that's imprinted on the tape so as long as it's played back on a similarly eq'ed playback machine, the eq should do it's job and the tape will sound the same as if it were played on the machine it was made on.
Please keep in mind that this post is still pertaining to playback only. We'll be jumping into the record side of things very soon.
NAB eq was developed in 1953. It has high and low frequency pre/de-emphasis. Also called IEC2.
IEC has been the European standard and only has high frequency pre/de-emphasis. Also called IEC1 or CCIR.
Well, it would be great if we could have our machines set up for IEC eq, put on a Tape Project tape and bam,.. perfect sound forever (gee, where have I heard that before?). Of course not,.. what were you thinking!
If you're a Charter subscriber you have or soon will have a Tape Project alignment tape. This is a calibration tape to do the adjustments to the heads that were outlined in the first few posts of this thread. These tapes were made on the same ATR's that our music tapes are made on  which eliminates one of those "If only they could have,.." wishes that keeps a playback media from being truly purist. With these alignment tapes we're able to align the heads and calibrate the eq to the machine that produced the TP tapes. I don't think that there's ever been any releases that can boast the same level of commitment to the purist ideal.
If you have the Alignment tape there are tutorials on the use of the test tones in the Tape Project Newsletter. If you haven't subscribed to it you should and copy them to a file on your computer to refer to as you use the tape. You'll also need a service manual for your machine to find out where to make adjustments. To subscribe to the Newsletter you have to take a trip over to the Tape Project home page;http://www.tapeproject.com/

So, what if you have a Technics or Otari with 1/4 track heads too. Can you use the TP alignment tape on that playback head too? Unfortunately no. For one thing these tapes are speed specific. You could use it for getting the adjustments close but then there's the tracks. Most alignment tape are done full track meaning the entire tape is recorded in one direction. But since these were recorded on 1/2 track machines with a 2mm guard band (space in between) and the tracks are offset on 1/4 track, the levels of the channels will be slightly different. Anyway, even if you could accurately do head adjustments on your 1/4 track head, this is an IEC tape and many of the adjustments are done with test tones that receive the correct de emphasis.
It's better to get the right alignment tape from MRL.http://home.flash.net/~mrltapes/
Title: Basic Recording 1
Post by: ironbut on November 02, 2008, 06:59:22 pm
By ironbut (http://profile.imageshack.us/user/ironbut) at 2008-11-02

Ok, the previous post on eq was kind of a warm up lap for this one. And even if you don't have any aspirations to drag your machine into the confessional of your local cathedral to "ride" the faders, this post will help fill in the voids in understanding magnetic tape in general. If you happen to have an owners manual you can probably skip the last part of this post since it should be easier to follow (being specific to your particular machine) and I won't be going into much more detail in this post.
To begin, we'll have a look at the controls and components to get you started and pushing that record button.
Connections To begin with, we'll record something off of a CD or record from your system. Bear in mind that sometimes the back panel connection of your tape deck and/or preamp can be a little confusing (manufacturers idiosyncratic labeling). On my Technics it's pretty straightforward. There are a left/right line output that is your playback output. You can connect this to any line level input on your preamp. The left/right line in are for connections for the record section of your machine. If you have a tape loop on your preamp, you're in luck since this preamp connection bypasses the active gain sections, volume/balance pots of your preamp. It's essentially a stereo patch connection so you don't even need the preamp to be powered up to send the signal from your CD players (or other source) signal to be passed on to the recorder. Just remember to set the input selector to the source you wish to record (on my preamp, you also need to throw the record switch too. Don't forget to switch this off when you're done or you'll be pulling cables and hair out while you try and figure out why you're not getting any sound). If you don't have a tape loop, you can connect any line level source component directly into the line in on the tape machines back panel (this includes phono stages). From a purist point of view, this is preferable since you don't have to send your delicate signal through a couple of switches and an extra set of cables.
Now we get to use the pictures of the Pioneer 909 that I "borrowed" from an auction ad.
Components Most modern reel to reel decks have a couple of amplifiers built into them.
1. Input amp
2. Playback amp
and many times;
3. Microphone amp
4. Headphone amp (actually just a the playback amp with a headphone jack)

Controls I'll only cover the ones that most machines will have.
The photo on the left show the controls for these amps.
-There's a single output level knob which will also control the output of the headphone jack (headphones are almost essential if you do lot's of recording). Just above the output pot is a pushbutton labeled Monitor. This toggles the output, between the source (CD, Phono?) and the tape (playback head). This allow you to "monitor" between the source (CD player) and the sound from the tape (playback head).
-In the middle is the mic input level (there are left/right mic input jacks to the left).  The setting for this pot depends entirely on the mic amp circuit design, the sensitivity of the microphones used, and the level of the sounds that you're recording.
-The control on the left controls the level of the line level input you connected to on the back panel of your deck. Too little signal results in a poor noise level (signal to noise ratio). Tape hiss is your noise level and with modern tape formulations, you should be able to record at a level that this "hiss" is barely noticeable. To find the correct level to record your CD you'll use the VU meters on your machine (the one in the picture is a digital bar type meter and you can see just a bit of it (blue).
VU Meter A standard VU (volume unit) meter has an arc that the indicator swings across. Somewhere to the right of center is a zone which starts with a large Zero and is printed in red. When you record, you don't want the indicator to hang out in that red zone for more than an instant and depending on the tape/record circuit you may not even want it to go into the red at all. Zero VU indicates the level at which the recording could begin to distort. On the other hand, you want the peaks on your music to be at Zero VU since it lifts the sounds you want to hear as far above the noise floor (hiss) as possible. Some experimentation is needed to find out just how much headroom (level above Zero VU you can achieve without distortion) with your particular tape/head setup. To get the most headroom and take advantage of the high output of modern tape formulations, your machine need to be biased for the tape you've chosen to use.
Bias When we talked about output eq in the previous post, I had to let you guys know that magnetic tape recording isn't perfect. I know, I know,.. BooHoo!  A simplified explanation of bias is that it's a high frequency signal that's added to the signal which lowers distortion and improves frequency response. The  level of the bias is tape dependent and manufacturers provide tables for these levels. Record gap length, tape speed and tape type determine the bias level.
For most home users, it's probably best to choose a tape that you want to use and have your machine calibrated to use that tape. Most machines have a couple of different setting for bias and eq which means that you can have more than one type of tape to choose from. If you look above the mic input level pot, there's two buttons. One is bias (two settings-in or out) and the other is eq (two setting- in or out) so this machine has the potential for four different tapes.
Choosing a tapeTo a certain extent, the upper limit on which tape to have you machine biased for will be determined by the machine itself. Some of the highest output tapes can't be taken advantage of by consumer level machines. Some of these are also more abrasive so it will increase head wear too. There's a lot to say for biasing your machine for RMGI 468. It's currently available, it's not crazy money, and it's recommended by Paul Stubblebine. Paul has the opportunity to test the tapes that are available and he's a real perfectionist. So, as Doc would say, this one's a no brainer (IMHO).
So, now we're set to use the picture on the right and record that CD.
After threading a blank tape onto the machine (make sure it's not "Waltz for Debby"!) and setting the bias/eq switches we want to check the line input levels.
Set the record mode selectors (two buttons above the line input pot) left and right to on. Most machines have these and they're a great safeguard. These should always be off unless you're recording. On some machines there's red warning lights to let you know that you're in record mode. When I demo TP tapes I actually put tape over the switches to keep folks from recording over my tapes.
Start the CD and find an spot where you think that the level is about as high as it goes.
Set the Monitor button (over the output pot) to source. You'll see the VU meters deflecting with the music now. Adjust the line input pot so the musical peaks just hit Zero VU.
Once you find a level you like, press the play+record+pause buttons (picture on right) at the same time.
Start the CD again and hit the play button. A red record indicator light should be lit and the reels a turnin.
Your recording now!
If you want to hear what the tape will sound like, you can push the monitor buttons again setting it to tape and the output will be fed by the playback head. Keep in mind that there's a time delay from monitoring the source or the tape. That's the distance between your record and playback head.
When you're done hit pause again (you could use stop but pause can stop clicks that occur sometimes with a sudden stop) then stop.
Unless you want to do some more recording right now, turn off those record mode selectors!
That's it. Some folks prefer the sound that tape gives digital recording so give your "creation" a critical listen.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: ironbut on January 07, 2009, 01:02:48 pm
Thanks for tidying things up Doc. I'd like to ask that members refrain from general posting in this and other stickies. It's meant as more of a learning tool than an area for discussion. I would like to welcome posts that will add to the better understanding of all aspects of tape recorders and recording.
Title: Further Reading
Post by: ironbut on January 10, 2009, 01:56:53 pm
Here's a list of publications from Jay McKnight of MRL test tapes fame (along with a host of other accomplishments while working for Ampex during the golden years). Although I haven't exactly quoted his works, much of the knowledge that I have regarding magnetic tape has come from reading them and following his postings on various online lists (Ampex, Studer, ARSC).
All of these papers (excluding one) can be downloaded from his website;http://home.comcast.net/~mrltapes/
These are only suggestions and given enough time, reading everything there is certainly time well spent.

"Master Tape Equalization" There's an entire section on tape eq but I think this and the " Revisited" paper are the fillet.
"Tape Recorder Reproducer Response with a Reproducer Test Tape" Excellent info regarding the use of test tapes and getting the best alignment with them.
"Flux and Flux-Frequency Measurements and Standardization in Magnetic Recording" If you wish to understand more about what happens at the head/tape interface, this is it.
"Speed, Pitch and Timing Errors in Tape Recording and Reproducing" Great study of the sources, magnitude, and effect of temporal errors.
"Biasing In Magnetic Tape Recording" If your interested in the recording end of things.
"Permeability of Laminations" This is the one not on his website (I don't think) but is an AES publication. You can find it by googling the title. If you're an AES member, it's the usual $5 to download, if not,.. shame on you! ($20) Just joking, but if you've gotten far enough to want these relatively technical papers, you'd do well to join and have access to all the great stuff that AES does all year round.
Title: Re: Beginners Guide to Tape Recorder Basics
Post by: steveidosound on January 24, 2009, 04:05:53 pm
In an effort to supplement Steve K.s excellent discussion of head types, I would like to cover all the basic formats of 1/4" tape here and also give a bit of an explanation of what you might expect playing tapes of another format than the machine is configured for.
I will not cover speeds here as that is pretty evident if it is wrong, except to say that the two most common speeds in the consumer world are
7 1/2 inches per second and 3 3/4 ips. The pro world has 30 ips. which is not so common, 15 ips. (very common) and 7 1/2. Some consumer machines for voice also included 1 7/8 ips. and 15/16 ips. Note that these are all sub-multiples of one another and raise or lower the pitch by one octave... sorry... on to formats...

I am going to try to be consistant with a few definitions that get tossed about:

1. track: a single recorded length of information on a tape. It takes at least one of these for mono sound and it can cover the whole width of the tape or 1/2 the width or 1/4 the width. It takes 2 tracks to produce stereo (left and right) There are typically 2 or 4 tracks on a stereo tape. There are 4 tracks on a 4 channel or quadraphonic tape.

2. channel: a discrete information carrying section of electronics, whether for playback or recording. Thus a 2 channel machine would typically have 2 discrete inputs, 2 level controls, 2 outputs etc. capable of handling 2 streams of information from 2 sources. To store them on tape would require 2 tracks. These may be related as in the left and right channel of stereo or not. A 4 channel machine would need  4 tracks .
In the studio world, 24 channels on 24 tracks on 2" tape was common for a long time.

3. gap - relating to tape heads -  This was covered by ironbut, but I will say again that this has to do with what portion of the available 1/4" tape width is recorded with what number of tracks. There is not a one to one correspondence between gaps, tracks and channels because in most consumer format tapes you can flip the reels over at the end and record the other direction making what was the bottom of the tape now the top and record the other "side" by repositioning where the gap(s) align on the tape. The term "side" is interesting because it is the other "side" of the reels as in turning over a record (or tape cassette) but it is always the oxide "side" of the tape facing the heads.

Tracks on tape:

full - We started here, but only in the fairly early pro world. 1 gap - full 1/4" tape width. 1 track on the tape. I channel of information. (mono)

2 track  or 1/2 track or "half track" -  In the consumer world, a mono format using a 1 gap head to cover half the tape width to record 1 track of audio (1 channel  mono) in either direction on the tape. Very common from the early 50s through the end of portable battery reel recorders in the early 70s.
In the pro world, a stereo format (The Tape Project Format) for master tapes. A 2 gap head covering the whole tape width to record 2 channels of information on 2 tracks in one direction only. Could be used for 2 unrelated programs in one direction, but to my knowledge never was.

4 track or 1/4 track  or "quarter track" - consumer or semi-pro standard for either 2 channels of information in 2 directions of the tape in an interlaced (see below) format using a head with 2 gaps centered on the 1st and 3rd "quarters" of the tape width from top to bottom, recording 2 tracks in stereo per side as in:
Track 1 = Left Side 1
Track 2 = Right Side 2
Track 3 = Right Side 1
Track 4 = Left Side 2
or 4 dissimilar tracks by recording program on one track at a time in the so called "4 track mono" format.

-OR- a 4 gap head recording 4 channels in one direction on 4 tracks for either the quadraphonic surround format popular in the 1970s or with the ability to use the record head to play back in sync, for early project studio "4 track" multi track / multi instrument use.

I guess I do have to mention that there was a format using an 8 gap head recording 8 tracks for 8 channels on 1/4" tape made by Fostex and to my knowledge no one else for the same semi-pro multi track project studio use as the 4 track machines above.

From all of the above, hopefully it will be more clear what happens if you play a 1/4" wide tape on a machine of another format than the machine which recorded it.
The basic rule is the head gap reads whatever portion of the tape it covers. If there are more tracks than one covered by that gap you will hear all of them, though not perhaps perfectly. Similarly if there is a wider track on the tape than the gap you are reading it with, you will still hear that tape track - but not perfectly as the head gap is not aligned with the center of the track.
A full track head, for a silly example, would read all 4 tracks on a 4 track tape or both tracks on a 2 track tape.
One channel of a 4 channel 4 track machine with 4 head gaps will read whichever fourth of the tape it is covering. So, you would hear the same thing from all 4 (more or less) if you played a full track, full width mono tape on it.

A word about interlaced and/or 2 direction formats -
This is where you can start hearing material backwards. Because they chose to interlace the left and right tracks (as explained above) on the most common consumer stereo 4 track format, if you play them on a  2 track stereo machine you will hear material from the other side of the tape backwards as the top gap of the head is covering the first quarter of the tape - which is the left channel forward from side 1, AND the 2nd quarter of the tape which is the right channel from side 2  backwards!
The bottom head gap is covering the other 2 tracks (3rd and 4th quarters of the tape), and gives you the right channel from side one combined with the left channel from side 2 backwards.

The other common related issue is playing a 2 track mono tape recorded both sides on a 1/4 track stereo machine. The left gap positioned on the top 1/4th of the tape will read the information from the top half of the tape (side one) whereas the right head gap of this machine will be positioned over the 3rd. quarter of the tape from the top and will read side 2 from the bottom half of the tape -again backwards.
The left channel of a 2 track stereo machine will read these mono tapes with the gaps properly centered, though the right channel will again be the other side backwards.
A  2 track mono machine would play only the left channel of a 2 track stereo tape and it would play side one left channel and side 2 right channel backwards of a 1/4 track stereo tape.

A  4 gap head on a 4 track 4 channel machine will play anything to some degree, though again, if you play any 2 direction tape recorded on both sides, either mono 2 track or consumer 1/4 track stereo, some of the channel outputs will have backwards audio from the other side. And none of the gaps will be properly centered for either 2 track mono or 2 track stereo formats.
Title: Print Through
Post by: ironbut on May 11, 2009, 03:06:40 pm
This discussion pertains to the a tape phenomenon that applies primarily to prerecorded tapes. It appears as an echo of music that can be heard during silent or quiet passages during playback. This is most noticeable in classical music tapes where the dynamic swing can be large from moment to moment as opposed to popular or jazz which is fairly "steady state" in loudness and has fewer passages with very low amplitude. The source of this sound is from the adjacent tape wraps below and above the the one that is being played. It occurs while the tape is wound on a reel.

Before we get into it, there is also Crosstalk. For our purposes crosstalk can sound very similar to Print Through but is entirely different in origin. On 1/4 track tapes (like the 4 track tapes you buy on eBay) it shows up at about the same volume levels (relative to the levels of the recorded signal we want) as Print Through but is in reverse. The source of this crosstalk is mistracking of either the record head/tape interface during production of the tape or mistracking of your playback head/tape interface. It's quite often the former especially on tapes that were produced in a less than ideal way (high speed duplication, poorly adjusted duplication machines, poorly slit tape stock). One way or another, the space between the tracks (guard band) is being breached.

For the purposes of this discussion, we will use the way that one of the Tape Project tapes arrives which is tails out. Tails out just means that the tape is stored on the reel backwards. That is to say that if you were to load the tape like your typical 1/4 track tape that you bought on eBay on the left, supply side, and play it as is, the sound would be in reverse. With the TP tapes as well as most 1/2 track tapes, you would load the tape on the take-up reel side (right) and rewind it before playing. One of the reasons for storing tapes in this way is Print Through.

As the earlier statement would indicate, this echo is sourced from either the length of tape that is immediately above or below a given piece of tape (when wound on the reel).
Pre or Post-Echo implies the source of the unwanted signal that can now be heard on the tape. For "tails out" storage, pre-echo would come from the layer of tape just below the tape in question and post-echo would come from the layer on top of the section in question. The reason that tails out is preferred is Print Through is stronger in the direction that the oxide, relative to the substrate (backing) is facing. Because of this, when a tape is wound tails out the dominant Print Through is Post Echo which is less obvious than Pre Echo.

As you might guess, this unwanted printing of the tape happens when the tape is wound on the reel and is not an artifact of recording or duplication. It would seem to occur with all recorded magnetic tape to some degree but knowledge of print through by the recording engineer and duplication facility (as well as tape manufacturers) can minimize it.

I've been meaning to write this for quite a while but to really understand what's going on here you have to look at the entire process of what magnetic recording entails at the molecular level. It took a good 3 months to get this stuff through my thick skull before I felt confident enough to distill it down to something that most folks can understand (or want!).
That said, there is lots of disinformation out there on the web regarding Print Through but it's usually pertaining to it's sources and the mechanisms associated with it. I'll do my best not to add to it.

For us (the end users) we only need to know how to minimize the level and prevent any further Print Through from happening.
Here are the key elements that determine the level of print through.

Tape Thickness-
This includes the thickness of the substrate (backing), the thickness of the oxide and distribution of the oxide particles on the backing.
  The thicker the backing the better. This actually has nothing or little to do with the backing itself but rather the distance.
  The thicker the oxide layer the worse. This is more to do with it's tendency to accept a magnetic print.
  The even distribution of oxide particles within the binder (glue) makes them more stable and less likely to accept a magnetic print. Higher oxide thickness also makes practical distribution  of particles less precise.

As you might guess there should be a "sweet spot" for the ratio of substrate to oxide thickness but this is hampered by the more practical matters of tape length (the thicker the backing/substrate the less tape you can get onto a reel) and what should be the primary aims of tape production- signal to noise, dynamic range and a relatively flat frequency response ( reducing oxide thickness increases high frequency output and lowers low frequency output).

Signal Applied to the tape-
The higher the amplitude of the signal printed onto the tape the more likely it is to be Printed Through. This is actually a combination of the physics involved and the biology of our perception of sound. There's no practical need to go into the details here. There are frequency dependent issues with Print Through ( related to tape thickness) but they are almost secondary to the frequencies that we are most sensitive to.

Practical Matters

A large amount of Print Through occurs within the first 48 hours of recording. Within this 48 hour period a level of Print Through is determined by the above factors . It could almost be entirely eliminated if tape duplication had some way of storing the tape for this period without intimate tape to tape contact. This time factor has a lot to do with the stabilization of the magnetic poles of each oxide particle and I won't bore you with the details (even though I have no problems with boring you with all this other stuff). Suffice it to say that reaching  equilibrium within the oxide particles is central to how all this works.

This is very closely related to the time factor. If you recall your high school physical science course, heat is just what we call the level of motion that particles are exhibiting. Or, at least this is what we're measuring (Larry and other scientists who are reading this may now cringe as one!). The magnetic equilibrium within the oxide particles is disturbed by the increase of heat (particle movement) making them more prone to any printing (change in orientation).

So,.. I did say something about Practical didn't I?

It's been often said that rewinding tapes that exhibit print through several times can reduce the level . This is true and the amount of improvement depends a great deal on how stable the particles of oxide are on a particular tape. It's been theorized that this is due to the bending of the tape and the friction applied to the particles. I'm not inclined to believe the bit about bending but the friction part is somewhat believable. Tests have concluded however that the momentary loss of intimate contact with the adjacent tape layer(s) is responsible for most of this improvement.

It is suggested that all recorded tapes be "exercised" once a year by rewinding and playing them. Regarding the Tape Project tapes, I would certainly do this even if you don't have your "dream" rig completely assembled yet. I'm thinking about getting a pad to keep with my tapes to remind me to do this with the ones that don't get a lot of spin time.
With older tapes I've found that the ones that I listen to quite often have seen some improvement with "exercising". One of the reasons that this exercising works with Print Through and not on the "wanted signal" is that Print Through is applied without the benefit of bias. Bias leads to particle orientation that is more stable and orients particles that are more stable in the first place.

Proper Storage- Keeping tapes in a stable environment is huge. The best temperature to store them is around 68 degrees F (20 C). It's been found that with every increase in temp. of 1 degree C that print through can increase by 0.14dB. This figure is measured in the critical first 48 hours but as you can see, it is significant.

There have been efforts to reduce print through in the past. One of the main techniques has been to use purpose made "Low Print" tape. These tapes were formulated to take advantage of the types of oxides and the "thickness ratio" that leads to less Print Through. These tapes were made for spoken word since, as you might imagine, a lone voice in a hall would make Print Through a pervasive annoyance. They were however, not suitable for music production.

Another technique that never really took off, from what I can tell at least, is called skimming. This is the application of low level erasure to remove the print through. It surfaced during my research for this post in an AES paper or two in the late 50's on a product called the "Echoraser" but like I said, it doesn't seemed to have gotten wide acceptance. This could be partly due to some anecdotal findings that the application of small magnetic signals actually increased the level of Print Through particularly with tapes who had been incompletely erased with bulk demagnetizers.

Title: Preventative Maintenance
Post by: ironbut on May 24, 2009, 01:08:02 pm
I did a little service visit to a Technics RS150x owner the other day and found that the tensioner bearings were in bad shape. One was grinding pretty badly and the other was all but seized up. This, combined with the effort of the tensioners to maintain the correct tensions was resulting in the tape speed being slowed down. Since I knew that the bearings had been in good shape not that long ago and the machine has been run regularly since then, the most likely problem was that the lubricant had been "flushed" out somehow.
Anyone who's read this Beginners Guide knows that keeping the tape path spic and span is critical for getting the most out of your tapes and preventing undue wear to them. I think that a little fine tuning of the cleaning process is in order.

I clean my tape path about every 10 tapes or so. My machine is currently located in a spot where I can get a really good look at all the guides and heads so it isn't that tough for me to see when I really need to do this. In between cleanings I can clearly see when there's a little oxide or dust building up and I just use a dry swab to get this stuff off. This keeps any loose particles of whatever off of the next tape(s) to be played and prevents dropouts.

When you do use a head cleaner, you need to respect it's ability to remove contaminants from whatever surfaces it comes in contact with. Some of them take a little while to completely dry and I can attest to this from a wonderful tape that I ruined by not letting the head cleaner completely dry before I played it.
After that bad experience, I always dip the Q-tip into the cleaner and then roll it on a paper towel or something so it's just damp. This minimized the drying time and prevents any possible run off that will end up where you don't want it (like in the bearings).

I always use the least powerful cleaner I can for the job. Following this thinking, I very seldom use head cleaner for rolling guides since they seldom warrant more than light cleaning. So I use alcohol for the tensioner bearings, the reversing roller and the capstan. It drys quicker than the head cleaner I use and is cheap-cheap-cheap. Of course the capstan is more likely to have some stubborn bits attached to it and you can feel these under the Q-tip as it rides the turning capstan.
Even though alcohol drys much more quickly, I still use a "just" damp swab for this cleaning.

The same thing goes for the pinch rollers. These do get dirty pretty fast and I use a swab dampened with just water and a swab damped with 409 cleaner alternately. There are rubber softening agents (Rubber ReNew) available that I use a couple of times a year. These products should be allowed to dry overnight.

Keep the areas around the tape path clear of oxide. You won't know if your tape is shedding excessively if there's always oxide there anyway.

Developing good habits for cleaning these machines is very important. You don't need to go overboard but it is important to look at what's going on.
Changes in the amount of oxide shed or parts wear are indications that something might be wrong with either the machine or the tapes you've been playing recently.
Bear in mind that excessive oxide shed may not be the result of your playing the tape. It could be the result of the previous playing, improper tape storage or the aging of the tape itself.

Title: Annual Maintenance
Post by: ironbut on October 01, 2009, 02:21:09 pm
It used to be that there were plenty of knowledgeable reel to reel techs in, at the very least, every major city. The shops where most folks bought their machines from would either have someone in house or someone that they used to service and maintain reel to reels. I used to have a buddy that used to have service contracts with several radio stations and sometimes I'd tag along as he serviced the tape machines, turntables and consoles around the area (very cool!). Some of you guys may have purchased ex-radio station machines that often have a sticker on it with the date of the last servicing, bias settings and the tape formula that the machine is biased for.
How often this regular maintenance was done depended on usage for the most part. But for the home user, it was usually an annual affair.

Well, here in the 21st century, you can still find those techs but you really have to do some searching. It's also important to use someone who's recommended by someone who knows. Many times a few calls to your local audio shops that were in existence in the 70-80's will result in someone who has the equipment and experience to do this kind of work will reveal their hiding places. Another good place to ask is pro audio shops.

To go back to our automobile analogy, many of the most important parts of your machine are mechanical. And anything on this planet that spins, slides or pushes against another object is subject to wear. Bear in mind, there's a big difference between something that has wear and something that's worn out.
The abrasive nature of the oxide side of a tape will grind down all fixed objects it comes in contact with. Of course the most common ones are the heads. But it also puts a flat spot on any fixed (non-rotating) guides or lifters. How long it takes for these worn objects to become a problem depends on the abrasiveness of the tape, the composition of the object in question and the mileage (we'll use this term since it takes tape speed into account as well as time).
As an example, the tape lifters are the arms that keep the tape from coming in contact with the heads during fast forward and rewind. This is meant to reduce head wear and prevent  playback of the tape during these functions. These can wear rather quickly since the contact area tends to be small and the tape speed across them tends to be high producing higher temperatures. Depending on how the machine was/is used will determine how much of a groove has been worn into the lifters. If, for instance, the machine has been used primarily for the playback of 1/4 track tapes, there may be very little wear since you don't really need to rewind these tapes very often (you just flip the full reel over or in the case of auto reverse, the machine just plays the B side automatically). But making sure that these lifters don't become too grooved is important since they contact the oxide side of your tapes and the groove edges can damage the tape edges and in some cases, if the tape "wanders", damage can take place further into the tape surface.
Some of these lifters can be rotated or a sleeve can be put over it since (in most cases) the diameter of the lifters can be increased with no ill effects (I put teflon tubing over mine and rotate and replace it when it becomes grooved).

The lifters are kind of a special case since they have no effect on the quality of playback.
The heads and guides are an entirely different story however.

As the heads or guides become worn, the way they contact the moving tape across them changes. For the most part, we just kind of live with the slow decrease in high frequency response until it's time to have the heads relapped. This change in frequency response is so gradual and slow, I seriously doubt that casual users will hear it's effects until it's pretty serious. Just like I said before, this all depends of usage so I can't tell you how often you might need to send your heads out but for most of us here, we're talking several years.
That is however, one of the things that a well equipped tech can do for you. He can use well calibrated equipment to measure record and playback response and let you know if it's time to have head work done.

Aside from doing measurements and adjusting for wear in the tape path, regular maintenance also includes cleaning of pots, switches, contacts and checking all the other adjustments. This includes your brakes, pinch rollers and tape tension.
These adjustments can be done in any order just as long as tape tension is last.
There are several different types of braking systems in reel to reels. The one that takes the most maintenance are the shoe and drum type (as on Technics). There are two small, felt brake shoes on an arm that rocks one way when braking clockwise, and the other way when braking counterclockwise. These shoes are raised to contact a drum which is an extension of the reel turntable to stop rotation.
The other type of brake which is common has the same type of drum but instead of having little felt shoes on a rocker, it has a metal band that's usually covered by a canvas like cotton material. The band is tightened to stop rotation.
Nice smooth braking is important since grabbing or chattering can ultimately stretch or even break delicate tapes such as acetate backed ones from the 50's-early 60's.
Brakes that are too loose or poorly adjusted can leave slack in the tape path which lower the tensioners and release the switches that allow you to engage the transport (you have to turn one of the reels to pick up the slack enough to engage the transport in this case).
Since the pads or bands are made of a material that wears, the brakes need to be adjusted to compensate for the loss of material. This can take years depending on use but depending on how exposed your brake drums are and other environmental elements (such as airborne contaminants), the drums may need occasional cleaning.

On my Technics, the drums are very exposed to dust and anything else that happens to be in the air. So, about once a year or so, I open up the back and top and clean them. I used to use alcohol but I find that something like window cleaner does just as well and I don't have to worry about it loosening the glue that holds the pads on or damaging the enamel coating on the drum surface (I think it's some sort of enamel?).
The procedure is very simple.
Take a piece of masking tape to hold down whatever tensioner/arm (in the case of optical switches tape over the light) to "fool" the machine into thinking there's tape present and the transport will work. Open the machine back or whatever it takes to access the back of the reel motors. On the parameter of the reel motor is a smooth surface (on a Technics, it's painted black). That's the drum. Take a q tip and lightly wet it with cleaner. Engage play and both reel motors should rotate with the brakes disengaged. Run the q tip on the surface for several rotations then dry the drum with the dry end of the q tip. You'll more than likely find that the q tip has collected some dark crap on it. Repeat this with fresh q tips till they come out clean.
Repeat this procedure on the other drum.
Allow the machine to play this way for about 5 minutes to assure that the drums are totally dry. Remove the tape and that's it.
Sometimes, right after cleaning the brakes might be a little tight or loose so take a junk reel of tape and work the brakes a few times. If it stays loose or tight, they need to be adjusted per your service manual. If they're still grabbing, the shoes/bands may be contaminated or loose and those will need cleaning or scuffing (depending on the material) which does require some disassembly.

The other major part of servicing is lubrication. For the most part, the bearings on your machine are sealed units and you should not attempt to lubricate them. Adding oil to a gunked up bearing will only loosen the hardened grease and you'll have to replace them anyway. But things like pinch rollers don't have ball bearings and can be removed and the surfaces cleaned and tiny amounts of oil can be applied. If you apply too much, the oil will run down the sides of the pinch roller and onto the tape contact surface (and you won't even see this if it's happening on the back of the roller!). The rollers are probably the only place I would recommend most home users to attempt lubrication. Just be sure and keep all those surfaces super clean and oil free. A tiny bit of oil on your capstan surface could ruin a tape fast!
There are adjustments that need to be made as your pinch rollers wear. Even contact and the correct pressure that the roller(s) exert on the tape/capstan interface prevents slippage or uneven wear on the capstan bearings.

Checking tape tension is important for both machine performance and the life of your tapes. It should be the last thing on the list of any adjustments are done that effects the tape transport (including head adjustments). You can do rough adjustments electrically but to take your tape path into account, you really need something like a Tentelometer which is properly calibrated to do it right. So, if you've done any tape path mods, had your heads relapped and/or adjusted, or made any changes to guides (rotating), your tension has changed. There is usually some wiggle room (+/- a given number of grams) so it doesn't mean that it's totally out of whack now, it's just changed.

Well, so that's an overview of some of the things that should be done on some sort of regular basis. I don't mean to scare you guys into thinking that you're ruining your TP tapes or that your playback is totally sub par, and for most of you, these things may not need to be done every year. But, it does need to be done sometime no matter which machine you own and since very few of us have all the equipment needed to do these things right, it pays to establish a relationship with a local tech who can get to know you and your machine.

As usual, if you wish to discuss the entries in this and other stickies, please do it in the regular forums so we can keep stickies free from discussion.
I welcome any criticism or reminders of stuff I just plain forgot. After all, these are meant to educate our members and not mislead them. Please PM me and I'll edit this and any other sticky if I find it necessary.

Title: Sticky shed binder change
Post by: ironbut on April 04, 2010, 11:40:02 am
This post is to supplement the previous post (#23) regarding sticky shed.
Over the years I've heard some explanations of why the tape manufacturers switched to the binders that resulted in Sticky Shed Syndrome and quite frankly, it all sounded like urban legends to me. Here's what sounds like the real deal from Dan Manquen who was working for 3M/Micom at the time;

"The main factor in new tape binders was to increase the ratio of
magnetic particles to "glue".  The stronger the binder, the less you
need.  High crosslink thermoset polymers offered significant advantages
in MPVC (Magnetic Particle Volumetric Concentration), yielding higher
outputs.  Old Scotch 111 type tape had about 40% MPVC, while later
high-output tapes got up to 60+%.  Some of the extra packing was also
due to the cleanness of the needle-shaped magnetic particles, referred
to as lack of dendrites (which are like branches on a tree.)  It is much
easier to orderly stack cord wood than tree trunks with branches still

Urethane glues are also tougher, providing longer life under high-wear

The use of the Phizer particle that gave an output boost for 456
required changes to the binder due to the chemistry.

The Achilles heel of the Urethane binders was that the long polymer
chains can break down in the presence of moisture, weakening the bond.

Dale Manquen at MANCO"
Title: Tape Mold/Milldew
Post by: ironbut on October 22, 2010, 01:44:04 pm
I received an email regarding the question of tape mold and upon searching our discussion of tape care here, I realized that I hadn't recommended anything but "toss it!" to the readers.
In most instances, I still recommend getting rid of any moldy tape, the storage box and the box it was shipped in too.
Of course, some tapes are worth the trouble it takes to clean them so here's some info on how to do this.

First, how can you tell if it's mold?

Mold appears on the outside edges of a tape which is visible through the windage holes on the side of the reel. It's a light colored dusty blotching that looks as if someone with flour on their hands handled the tape. There's an excellent photo included on pages 3&4 in the research paper who's link is below.

The major issue with mold is the spores. The spores are used by the mold to migrate and are carried by the air. Playing or worse, rewinding or any fast winding of a moldy tape will spew these spores everywhere and contaminate the room, it's contents and particularly, the machine it's played on. Every tape that's played on this machine is potentially contaminated until it can be thoroughly cleaned. The room should also be vacuumed a couple of times.
Always wear a particle mask when dealing with mold. We may not be dealing with much, but it doesn't hurt.

As far as cleaning the tape, I've taken the liberty to cut an paste the recommendations of Marie O'Connell who posted here a while back.

1) Keep these tapes away from any other tapes.
2) Don't play them on any machine that non-moldy tapes will be played on.
3) Remove the metal flange and carefully soak in some Hydrogen Peroxide (the flange, that is!)
4) Lightly vaccum with a Hepa cleaner the first side of the pancake.
5) Lightly soak a cotton ball with Hydrogen Peroxide or Isopropyl Alcohol (more than 91% pure) and lightly wipe the tape edges in a circular motion.
6) Repeat this on the other side.  You will have to use a spare reel whilst the moldy one is being treated.
7) Using a dedicated machine, cover the heads with pellon and run the tape through this, fixing any splices as you go. (... take the machine out and away from other equipment, like in the garage).

This post was regarding a tape with sticky shed to complicate matters so you could use a cleaning tissue (pelon) before the tape enters the head nest.

Here's the best research I've found regarding the issue of tape mold. It was conducted using acetate tapes so bear that in mind. If you choose not to read the entire pdf at least look at the photos of molded tape on pages 3 and 4.
The pdf is at the bottom written by Jim Thurn.


Title: Measuring Head Impedence
Post by: ironbut on July 21, 2013, 02:50:52 pm
I had done some searching for how to do this measurement in the past and always given up.
Thanks to Rick Chinn on the Ampex list, finally have the procedure.
Haven't tried it yet but here it is.
Thanks Rick!

The head is an inductor, so the impedance varies with frequency. I think 1k is the usual frequency for a head. If you can find some old Nortronics lit, you'll see what they used.
You can measure impedance using a signal generator and an ac vtvm, like an HP 400EL/FL or one of the older models.
The generator needs to have a known output impedance. 600R works well.
you connect the generator to the ac vtvm, and you adjust the output for a known reading on the vtvm, say like -10dBu. (I wouldn't drive the head too hard, and you definitely don't want to saturate the core).
Then you connect the head across the input of the VTVM and note how much the output drops by. From this, you can calculate the impedance.
Assume 600R generator impedance. If you're working in dB: then Z = Zs * ((10^dB)-1) If you're working in volts,
then Z = Zs * ((Vunloaded/Vloaded)-1) Example:
you set the meter so it reads -10dBu, with the generator at 1khz. then you connect the head, and the meter reading drops 1dB
then, with your handy dandy calculator (or spreadsheet), you find 10 to the 1th power, which is 10, and then subtract 1, leaving 9.
Then you multiply the source impedance of the generator by 9, giving 5k4-ohms.
If you work in volts, then set the meter so it reads 100mv, with the generator at 1khz. then connect the head, and the meter reading drops to 90mv.
then, 100mv/90mv = 9, subtract 1, and get 8. then multiply the source impedance of the generator by this, 600R * 8 = 4k8-ohms. The head impedance is 4800R at 1khz. (I picked numbers out of the air, so I didn't think that the answers from the two examples would agree, and they don't)
Of course, you can sweep the generator frequency to see the change in impedance with frequency. If you can sweep over a far enough range, you'll see the head's self-resonance, although this is influenced by the source impedance of the generator and the capacitance of the connecting cables. To really see this, you need to raise the source impedance of the generator considerably, so the generator impedance has less influence on the resonant circuit formed by the head, the cable capacitance, and the head's stray capacitance.
This method works with other things than heads.