Some help with Revox B77 Mk2

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Rewinder

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Hi everybody. I have a B77 I purchased in 1982 that was not used much. The last time was 10 years ago. Now I want to put it back into action – I missed the old sound. Even though the deck still sounded good, I want to do an overhaul. There are three problems that I need help on.
1 Where can I purchase the mechanical counter toothed drive belt (I don’t know the part #), and the rubber ring belt part# 31.99.0106.
2 The tape slows down near the end when it’s in rewind or fast forward mode.
3 With loaded tape, the deck goes into ‘play’ when I turn the power on. I tried a couple other things while analyzing the problem and found that if I slide the ‘editing lever’ to the left (locked) and turn the power on, then it’s OK, the deck does not go into ‘play’.
I did a search for help on the forum before I posted but did not find anything.

Thank you
Rewinder
 
Ive always lusted after these machines but could never afford one :(
 
1. The belts should be available on ebay.

2. I have the slow-winding problem myself. I'd love to know how to fix that too, replacing the motor capacitors hasn't helped. In my case, I'm convinced it's something central, like the power supply, but short of changing the PSU capacitors out I'm not sure what to try. It would be nice to get that machine working reliably again.

3. I have heard of the Play problem, but I can't remember the solution. I seem to recall one suggestion was that it may be a fault in the logic board, likely the PROM which the system uses as a truth table for the transport logic. It may, however, be something simpler like a bad capacitor or the PSU not delivering enough juice and confusing the logic.
 
Rewinder said:
Hi everybody. I have a B77 I purchased in 1982 that was not used much. The last time was 10 years ago. Now I want to put it back into action – I missed the old sound. Even though the deck still sounded good, I want to do an overhaul. There are three problems that I need help on.
1 Where can I purchase the mechanical counter toothed drive belt (I don’t know the part #), and the rubber ring belt part# 31.99.0106.
2 The tape slows down near the end when it’s in rewind or fast forward mode.
3 With loaded tape, the deck goes into ‘play’ when I turn the power on. I tried a couple other things while analyzing the problem and found that if I slide the ‘editing lever’ to the left (locked) and turn the power on, then it’s OK, the deck does not go into ‘play’.
I did a search for help on the forum before I posted but did not find anything.

Thank you
Rewinder
Click to expand...


Ive always lusted after these machines but could never afford one ;)
 
Thanks jpmorris for the info, I found several suggestions as to what may cause the "play on power up" problem, but nothing to say it was ever fixed or how. I have the service manual so I'll check those circuitry to start.
On the counter drive belt, it looks like Ebay-UK would be the best shot. BTW, where in the manual do I find a picture or part # for that counter drive toothed belt?
On the "tape slow down" problem it is suggested to be "tape shed". I,ll have to bake some tapes - food dehydrator - and clean the tape path.
Rewinder
 
I got the counter belt kit from e-bay in the UK. The seller even sent instructions how to install them. pretty good buy.
Does anyone know where I can get replacement capacitors for the B77 motors. ITT MP-33/4.3uf/160v, ITT MP-33/3.5/160.
 
Rewinder said:
I got the counter belt kit from e-bay in the UK. The seller even sent instructions how to install them. pretty good buy.
Does anyone know where I can get replacement capacitors for the B77 motors. ITT MP-33/4.3uf/160v, ITT MP-33/3.5/160.
Click to expand...

This guy has been able to get new ones made:
Revox Tape Parts NEW Motor Capacitor SET FOR A77 B77 PR99 | eBay

You have to import them from Australia unfortunately, but there you go. Sadly that wasn't the cause of the slow winding problem on my deck.
 
Hi JP, beside the problem of "playing on power up" I'm also having random scratchy noise when I record. So I've decided to change out all the caps, starting with the power supply and transport control boards. Later on I'll look at the audio circuitry - right now I don't think that's the main problem.
I'm making a list of the capacitors that I want to change out now, but it's a little difficult matching the replacement components and finding where I can buy them. But I love the challenge, it gets the old retro brain tinkering again. I saw that Australia Ebay seller, and also checking out Mouser.
Rewinder
 
If I remember right, that seller in Australia sells a kit which contains the complete set of capacitors for a B77.
 
Hi JP,
Update on the Revox B77. I bought the kit with the complete set of caps and pots plus the capstan motor oil from Australia. He emailed me some service documents also that I found necessary. I received the package in 14 days. Not bad at all. The seller gets 5 stars.
I started swapping out caps last night, which will take some time.
One question; what kind of adhesive or glue can I use to hold down the 2 large caps on the power supply PCB? I think its called component adhesive. Would HD or Lowes sell it?
Rewinder
 
Do they need it? I'd rather not open up the machine but on my spare PSU board they just seem to be soldered in with no extra supports.
 
The old caps were glued to the board on my PSU. They were not very difficult to pry off using a flat head screwdriver or 1" scraper.
In the Service Sheets from Peter (Australia) he recommends that those caps be glued to the board.
 
Well, this is 2 months later and I have an update. First I changed out the caps on the Transport boards and that took care of the "go-into-play-on-power-up" problem. So the fix proved it was a bad cap. Problem is I had to remove all the boards, change the caps then re-insert all the boards before i tested the deck, so I cannot specify which board or cap links with the problem,too bad.
I also changed the caps and pots on the Audio boards that cleaned up some static on all the Input and Output circuits especially the Record and Monitor amps.
I would say a job well worth it.
I have a new problem, I now need to replace the brake lining.Seems like time finally took its toll on them after all these years. Now I need to find a place to get new lining, any ideas.
Howie
 
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