Quote:
Originally Posted by dave
"Ian Bell" wrote in message
news:44f0794e.0@entanet...
My high speed A77 is running too fast. The service manual description of
the
capstan servo talks about a resonant circuit used as a discriminater but
the circuit shows an NE555 instead. It's an old A77 and the capstan servo
PCB looks like is has the resonant circuit - no sign of the 555. I have
gone back through capstan servo circuits at the Studer web site and the
only one with a resonant circuit is in the A80.
So I don't have a definitely correct circuit for the capstan servo - need
advice on how to diagnose & fix this problem.
Cheers
Ian
Ian, I can send you a scan of this circuit, it's the older version of the
speed control (1.077.725).
Decode my email address and let me know where to send it.
Dave
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I had the same problem yesterday. I repaired the A77 myself as I have the service manual. I bought the manual together with the machine in the early 70's.
The culprit was the 220uF 6V elco which forms the damping circuit after the frequency
discriminator on the capstan motor control board. The elco went very low resistance, about 400 Ohms........ Replacing the elco made the machine work OK again.
Kees