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I need to replace the 'time bomb' 0.47 caps on my Revox A700 and want to know the easiest way to access the electronics - front or back? I have the service manual but it's a bit confusing ... TIA. Michael
Follow Ups:
Both of my A77 machines have gone up in smoke. Since the 'time bomb' or 'firecracker' caps are on the drive board, the first symptom of defective caps is that the tape drive stops. Then billows of smoke come out of the machine. The culprit is usually one particular cap on the motor board (see image). The case cracks and the cap smells. They are usually visually identifiable.
I have successfully replaced all of these caps on both A77 machines, and they work perfectly. So Inmate51's assumption that I don't know what I am doing is wrong. I was simply asking for help to locate the boards in question, as I have never worked on A700 electronics.
I have also completely disassembled the take-up reel mechanism on the A700 to replace what seemed to be a missing washer which was causing the reel table to ride up on its shaft.
And finally, I have entirely rebuilt a Hammond AO-29 amp which required a new transformer, new (substitute) electrolytics, etc.
That said, has no one here worked on an A700?
Which version of the A77 went up in smoke? Mk II, Mk III, Mk IV?
Mine is a Mk IV from about 1978-79 or so, and is working fine. Maybe when I sent it up to Steve Smith in Nashville, he replaced those caps and just didn't say anything about it.
With regard to the A700...
The A700 never really made it into the mainstream of Studer Revox decks, which may be why you're having a hard time finding someone who's familiar with servicing it.
I briefly worked with an A700 while I was studying music and audio in Montreux, Switzerland in 1974. I think that's when Studer Revox first introduced the product. It looked very cool, and had an A80 sort of look to the tape transport. I was not impressed with its performance or build quality. We used it maybe three or four times, and went back to our other decks.
Seriously, if you need assistance, Nashville still has some professional Studer techs around - ya just gotta make a few phone calls.
:)
The first to go up in smoke was an A-77-III two-track used by a radio station. I found the cracked 0.47 cap, and replaced it and three others of its type. The machine now works perfectly.When I ordered the replacement caps, I actually bought eight of them, anticipating the same issue on my A-77-IV four-track. This was a machine I purchased new in 1974. Late last year, this machine also went up in smoke. I replaced the four 0.47 caps and it now works fine.
Now I need to replace eight of the 'time bomb' caps in the A700. These are located on the relay board, spooling motor control, and capstan motor control.
I have the service manual, but the instructions on how to find these boards/locations is not clear.
Can someone who has worked on the A700 steer me in the right direction? I will try to make a few phone calls ..
Edits: 07/15/15
"I will try to make a few phone calls .."Finding pro techs in Nashville is easy.
Google "Studer Revox Nashville"
Edits: 07/15/15
Finding pro-techs in Nashville is easy. Getting answers for free is not always easy. That's the idea of these groups. Lee Hazen spent many hours sharing his extensive knowledge helping tape enthusiasts solve their problems (see link below). The amateurs in turn sent their unwanted equipment to Lee as payback. Because of his physical condition, Lee, unfortunately, is unable to continue doing this. I personally always share my experiences - limited to the Ampex A series, Tascam 22-4, and Revox A77 - with fellow tape enthusiasts.
Mine was (emphasis,was) a Mk. IV Dolby.
"I need to replace the 'time bomb' 0.47 caps on my Revox A700"
How do you know that?
Not to be harsh, but if you think that some particular component needs replacing and you can't figure out how to access it, maybe you're not the guy I'd want working on my Revox. Find somebody in Nashville, and send it there.
:)
I thought everybody knew about them. My tech calls them "firecracker caps." Several exploded in my Revox A-77 before I got them all replaced. That was before the thing caught on fire.
On the other hand, my still pristine-looking A77 Mk IV has had no such issues.
About 10 years ago (mid 2000s), I sent it up to Nashville for a couple of minor physical repairs (brake bands, slightly bent reel spindle), and had a head alignment and electronics check-up, and it's all at or better than factory spec. There was no discussion about "firecracker caps".
Well, good luck and keep an eye (and ear) on it. You'll know when (and if) it happens.
Or not..
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