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Author Topic: A77 standard & pro - tech questions  (Read 3075 times)

Offline thomasdf

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A77 standard & pro - tech questions
« on: February 22, 2014, 06:16:37 am »
Hello

I may get a non working A77 pro on Monday. I know for fact that one of the reel motor is dead, but I have a few other A77 that are non working, so here is my question :

Is the reel motor on the Pro version the same that the MK1 or 3 A77?

Is the power supply the same too?

Thanks in advance,

Thomas

Offline ironbut

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Re: A77 standard & pro - tech questions
« Reply #1 on: February 22, 2014, 02:01:46 pm »
Hey Thomas,
I'm not an A77 expert but matching up motors can usually be done by part number.
So once you have all the machines in one place, compare them.
Also, check your service manual. Sometimes there will be footnotes that tell when parts have been changed over the years.
Bear in mind that on some machines, the take up and supply reel motors are different. This can become painfully evident when the mounting brackets won't line up!
steve koto
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Offline thomasdf

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Re: A77 standard & pro - tech questions
« Reply #2 on: February 22, 2014, 02:49:36 pm »
Thanks for your answer. I was asking because I just CANNOT find the A77 Pro service manual online. I have the regular service manual but there is no mention of the pro version in it.
Studer's FTP doesn't have it too... I don't even know if it exists :)

I have a found a A77 pro for 90? and I am not sure if I should buy it... It doesnt turn on (I guess that's no big deal if the PSU are the same on all A77) and the right reel motor is hard to turn (this is not brake related). The guy also gives me with it a dead A77 mk1 with lots of missing parts on it but (one reel motor, repro head, pinch roller) but I guess I could salvage one reel motor from it, and maybe the PSU if it is more than just a dead fuse.

Does it look like a good deal to you guys? I am very tempted because the A77 pro seems to be pretty rare, and I'd love to use it. (by the way, is it normal that there's no gain pot on the front plate for the pro A77? How does one set up the input gain?)

Cheers

Thomas

Offline ironbut

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Re: A77 standard & pro - tech questions
« Reply #3 on: February 22, 2014, 03:38:42 pm »
To be honest, I'd never heard of the A77 Pro model until you mentioned it. The lack of any special support and the lack of front panel controls may be clues though.

My WAG is that this was a machine that was targeted at folks who were doing things like surveillance, security or other similar activities.
For the most part, these would be internally set and used with outboard mixers.
Some could have extremely slow speeds and might be record only.
These types of machines would be based on whatever the current production A77 was and customized to the application.

If this is indeed the case, these machines would not be considered rare but might only seem that way since once they've finished their jobs, they would be scrapped.

Personally, I wouldn't buy it if it was $10. But, I've already got some dead machines collecting dust.
steve koto
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Offline thomasdf

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Re: A77 standard & pro - tech questions
« Reply #4 on: February 23, 2014, 05:07:13 am »
Well there were SLS A77 as for Super Low Speed, very very low speed allowing up to 24hours of recording and stuff..

But the A77 Pro is another animal : XLR Input and Output, 7,5 & 15 IPS speed, it was clearly aiming at the professional recording studio market. You can only record from a line input or the tape itself...

Many people swear by it as being a great deck with a really good sound to it... That is why I am very tempted, being a sound engineer trying to add some warmth to my work ;)

The bummer is that it's really hard to find informations about this model...

Good informations about a few different models here (including the professional)

http://www.theimann.com/Analog/A77/Spezial/Professional.html [nofollow]

I am still wondering if the Pro & Regular share the same PSU and Reel Motors
« Last Edit: February 23, 2014, 05:11:35 am by thomasdf »

Offline ironbut

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Re: A77 standard & pro - tech questions
« Reply #5 on: February 24, 2014, 02:27:46 pm »
I'd steer clear of machines that finding info about is really tough. Fixing and finding parts will probably be even tougher!

If you'd like a high speed machine, I suggest you give up on all the Revoxes and buy yourself something like an Otari 5050 series machine.
Unbelievable bang for the buck and resources for parts and repair are about the best for any single semi pro machine out there.
steve koto
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Offline thomasdf

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Re: A77 standard & pro - tech questions > putting a A77 Pro back to business
« Reply #6 on: February 24, 2014, 04:35:39 pm »
Well I bought it tonight, before I see your post.
Still, Studer & Revox parts are easy to source here in Europe, whereas with Otari it's a real pain to get spare... I even have 2 dead A77 at home in which I can take some parts.

On the A77 Pro I just bought, the reel motors are fine and fonctionnal, the sound is going in and out. I fixed the PSU problem in 5min, but now I get to the main problem :

When I switch the power on, the capstan motor starts and then slowly stops... When I re-launch it with hands it turns and then slowly stops.

I think this has to do with the speed regulator, I'll check the PCB Card one of these days as it is getting pretty late now here in France.

Best,

Thomas
« Last Edit: February 24, 2014, 04:37:40 pm by thomasdf »

Offline ironbut

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Re: A77 standard & pro - tech questions
« Reply #7 on: February 25, 2014, 02:14:10 pm »
Try just leaving the machine on overnight. Could just be an old cap.
Check to see if the capstan motor is the same as on one of your other machines.
Sometime companies will add a sleeve to the capstan shaft to double the speed on the standard motor units.
If this is the case, you may be able to troubleshoot the motor by plugging it into a machine that's working correctly.
steve koto
 Sony scd 777es(R. Kern mods)> Vpi Aires>Dynavector XX-2mkll>Bent mu>CAT ultimate>CJ premeir 140>Magnepan 1.6qr(Jensen xover)Headphone Eddie Current Zana Deux>AT ad2000,HD800 ,Metric Halo ULN-2 (battery powered),
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Offline thomasdf

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Re: A77 standard & pro - tech questions
« Reply #8 on: March 02, 2014, 05:43:03 pm »
Thanks! These are precious pieces of advice!!

I started a thread on the Gearslutz forum in which you may be interested :

http://www.gearslutz.com/board/geekslutz-forum/909090-revox-a77-pro-regular-version-technical-questions.html#post9905012 [nofollow]

Best,

Thomas