Revox A77 Refurbishment - Where to Start

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gerardv

gerardv

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Joined 2012
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#1
In an act of pure diyAudio folly I have started down the reel-to-reel rabbit hole. As a earning project I have a Revox A77 Mk2 that works but has definite issues. Reading around the web suggests starting with a full re-cap. But I'm wondering if there are any other things to do prior to the recap that might help further down the road. Or do I just go to Peter at nagarvox and get a recap kit?

Currently the machine:
Plays audio
One channel is faint
During operation "things stop" e.g. VU lights switch off, (I suspect PSU issues)

Are there any actions you'd advise me to take before starting the recap.
 
#2
I suggest fixing the issues first before doing a total replacement of all electrolytic and Rifa film caps. When recapping, do one board at a time and check for correct operation. This makes troubleshooting easier.

Faint audio may be a dirty potentiometer. Power dropping out may be an intermittent connection. I assume you have the wooden case with the power safety plug. To operate the machine without the case, you will need to make a pair of pins that plug into the sockets. If you don't have it already, download the service manual. It's very thorough.
 
#3
Thanks. I do have the service manual. I guess my concern here is that the issues it has might in fact result from stuffed capacitors. So I have two options 1) fix then recap, 2) recap and then fix. I'm concerned that either path will lead down a debugging rabbit hole if, for example, I start debugging but its the caps that are stuffed, or if I replace the caps but there's another problem I needed to fix.

(Short version: I'm nervous to start). Guess I'll start with the PSU and test/servcie that and see where that leads.

Thanks for the safety note too - those are really appreciated.
 
#4
The issues you mention are not necessarily consistent with capacitor failure. Try quickly turning the balance control back and forth to see if that alters the level of the faint channel. If so, clean all the pots with a spray cleaner. Is one channel faint when you feed in a signal on the inputs and monitor source, or when playing a tape. If only when playing a tape, it could be a dirty playback head. The outer track on the head is hard to reach with Q-tips.

Is it just the meter lamps that go out or is it more than that? The lamps are in sockets that get oxidized and go intermittent. Try prodding them with an insulated probe (like a pencil). Clean the lamp bases and sockets with contact cleaner.

The logic for fix then refurbish is that if you start with a functioning machine, troubleshooting is easier when you do the recapping. The amount of disassembly required when recapping makes it easy to make mistakes. Lots of connectors to reattach...
 
#5
blinker said:
The issues you mention are not necessarily consistent with capacitor failure. Try quickly turning the balance control back and forth to see if that alters the level of the faint channel. If so, clean all the pots with a spray cleaner. Is one channel faint when you feed in a signal on the inputs and monitor source, or when playing a tape. If only when playing a tape, it could be a dirty playback head. The outer track on the head is hard to reach with Q-tips.

Is it just the meter lamps that go out or is it more than that? The lamps are in sockets that get oxidized and go intermittent. Try prodding them with an insulated probe (like a pencil). Clean the lamp bases and sockets with contact cleaner.

The logic for fix then refurbish is that if you start with a functioning machine, troubleshooting is easier when you do the recapping. The amount of disassembly required when recapping makes it easy to make mistakes. Lots of connectors to reattach...
Click to expand...
Thanks, mate. This is the advice I was needing. I'll go down this path over my Xmas break and thanks for your ideas.
 
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