[B]I Need Some Help With A Revox A77[/B]

[teeformusic]

I Need Some Help With A Revox A77

I'm hoping someone here can help me figure out a problem I'm having with my Revox A77.

It is a Revox A77 Mark III professional version half-track with 15 1/2 and 7 1/2 ips speed. It has been a great machine for many years. I haven't used very much lately but I wanted to fire it up and maybe play some of my old masters.

When I powered up everything seemed fine until I discovered that one of the channels was not reproducing playback. I tried it with phones and also the RCA outputs to the amp. It seems that channel 2 is shot at least in playback mode.:scratch2:

I pulled it apart and switched the playback cards (after cleaning them with contact cleaner) and the same problem exist. :sigh:

If the problem is not with the playback pcb, where should I look next?

Any ideas or help would be appreciated.

 

[jwrosenthal]

When I got my first A77, I got it for a song as one channel was dead on playback (but on record you could see both meters moving). After several minutes of "scrubbing" the heads with alchahol and Q-tips (they were filthy even though they looked clean), it came back to life. The dirtiest parts was at the edges, and that seemed to be causing the problem.

James R.

 

[teeformusic]

When I got my first A77, I got it for a song as one channel was dead on playback (but on record you could see both meters moving). After several minutes of "scrubbing" the heads with alcohol and Q-tips (they were filthy even though they looked clean), it came back to life. The dirtiest parts was at the edges, and that seemed to be causing the problem.

James R.

Thanks for the advice James. I cleaned the heads thoroughly but it didn't correct the problem.

I think it may have something to do with the volume pot or the balance pot.
One side is working even without a tape on the reels. You can hear pink noise if you put on a pair of headphones. The other side is dead.

Is there a capacitor on the volume pot or balance pot that has dried up?

 

[guiller]

Perhaps you can find something useful here:

ftp://ftp.studer.ch/Public/Products/
http://www.hifiengine.com/manuals/revox/a77.shtml
http://www.eserviceinfo.com/index.php?what=search2&searchstring=ReVox+A77

All the best

 

[teeformusic]

Perhaps you can find something useful here:

ftp://ftp.studer.ch/Public/Products/
http://www.hifiengine.com/manuals/revox/a77.shtml
http://www.eserviceinfo.com/index.php?what=search2&searchstring=ReVox+A77

All the best

Good stuff Guiller! Much appreciated!

 

[teeformusic]

Still haven't figured out my Revox A77 problem.

I'm not sure where to look next.

 

[Wilburchubs]

Have you tried rotating the switches for the verious output options on the two knobs under the meters,also the 2 under the tape transport switches,know mine can be a bit tempremental(the switches,not the level knobs in front of them)

 

[teeformusic]

Have you tried rotating the switches for the verious output options on the two knobs under the meters,also the 2 under the tape transport switches,know mine can be a bit tempremental(the switches,not the level knobs in front of them)

Thanks for the info Wibur. I tried rotating the switches and even cleaned them with contact cleaner to no avail.

 

[jwrosenthal]

If you switched the boards, cleaned the heads, cleaned the pots, and verified that all the caps are intact, then it's time to send it off to Tennesse for the handicraft of JMTechnicalarts. As far as I know, he is the Revox go-to guy as he was the last certified ReVox service center in the US and apparently still has a large cache of parts (and the experience and knowledge to sleuth the problem). I've learned from bitter experience that if I can't figure it out in less than a couple hours, then it's time for a professional to step in.

Considering what a clean A77MkIII 1/2 track high speed sells for (the rarest of the rare as you know) with unknown use and service history, it's well worth your money to get a full service for your machine as you can't replace it for anything close to what it would cost for a rehab. Plus you know how it's been treated unlike anything else you could buy. I know it's not the answer you wanted, but I would go for the pro-service....then you are good for another 35 years!

James R.