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Author Topic: Just got a A77 MKIII - mods & tweaks  (Read 2792 times)

Offline thomasdf

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Just got a A77 MKIII - mods & tweaks
« on: February 12, 2014, 02:57:22 pm »
Hello everyone!

I just bought a Revox A77 MKIII 2 tracks for really cheap a few days ago (60euros). It was in working condition, but I gave it a good clean from the inside to the knobs.
Looks good and plays pretty good too, even tho I am thinking of recapping it pretty soon (L & R channel are not perfectly matched).
I have a few questions for you connoiseurs :)

Is there a simple way to make it run at 15 IPS? Right now it is  3 3/4 & 7,5. I know there's a trick with the 60hz power, but I am in Europe... so 50hz here...
If there's no simple way, I am fine with 7,5 IPS for the moment.

Does anyone have more informations about bypassing the line/mic input to improve the overall sound of the unit?

What tape would you recommand? From what I read, it appears that LPR35 is a good bang for the buck.

I am planning on using it right after my summing box, before going back to Protools thru the repro head, and from what's I've heard right now it's working pretty well in that setup.

Thanks a lot in advance

Cheers

Thomas

Offline ironbut

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Re: Just got a A77 MKIII - mods & tweaks
« Reply #1 on: February 13, 2014, 10:31:56 pm »
Hey Thomas,
Welcome to the forum.

Sounds like you found a nice machine.
It could be that the channel imbalance is has nothing to do with the capacitors. It's just as likely that head wear, alignment of the tape path or adjustment is the source of the problem.
Of course, that's not to say that it isn't one or more caps that needs to be replaced but these machines do take some regular maintenance to be at the top of their game.

IIRC the tape speed change requires a different capstan motor. It would be very tough just to find one.

Overall, I suggest that you get the heads checked out and the machine fully serviced. When serviced, you can get the machine set up to get the most from whichever current production tape you like.
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: Just got a A77 MKIII - mods & tweaks
« Reply #2 on: February 14, 2014, 10:22:10 am »
Hello

Thanks for your answer. I am in the process of getting another A77 (mk1 this time) as well as parts of a A77 (unknown version for the moment), so I guess I'll have some spare parts haha.
The head are like new to my eyes, they show very little wear. I have not demag them yet but I'll do that ASAP.

I can also take care of the recapping and I have already found an elegant solution to bypass the preamp and get the signal directly to the record amp thru pad resistors so I can run hot signal to the tape (master mix after a summing box or mixing desk), only by looking at the schematics...

I am amazed by the design of these tape recorder... Cristal clear, and really really solid. I need to get my soldering iron out now and do some testing.

I will keep you posted if you are interested in this project

I also have the opportunity to get for really cheap a non working A77 pro... Are the parts compatible between these? I know the tape speed, record and playback amps are different, but what about the brakes, VU circuits, heads, oscillators?

Offline Listens2tubes

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Re: Just got a A77 MKIII - mods & tweaks
« Reply #3 on: February 15, 2014, 07:14:45 pm »
I recently saw HS boards for an A77 on ebay. Not sure if the seller also was offering the capstan. From what I have read it is not so simple as just a simple parts change. Voltages are also different in the HS version.
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Offline thomasdf

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Re: Just got a A77 MKIII - mods & tweaks
« Reply #4 on: February 16, 2014, 02:23:20 am »
Ok, I'll see if I buy it and then I'll figure this out. The service manual is really well done so I'll try to find a way to fix it.

Offline ironbut

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Re: Just got a A77 MKIII - mods & tweaks
« Reply #5 on: February 16, 2014, 01:16:51 pm »
If you're using this deck to add a little analog warmth to Pro Tools, you may be better off with the slower speed.
I would print a taped and non taped version, line them up, and mix the two. You'll have better control over the amount of warmth you add if you use a printed track in parallel.
Doing lots of modifications may remove the distortions that you're trying to get.
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),
 HE Audio Jades