[TimPerry]

Ian Bell wrote:
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

have you verified that reel supply and takeup tensions are correct or at
least close?