[Ian Bell]

Audix wrote:

Ian,

I can't help with a fault diagnosis, but the circuit diagram you need
is 1.077.725 for the discriminator version. As you have doubtless
found out, the service manual available on the Studer website only
lists the later version 1.077.724 which uses a 555.


Yes, managed to find a circuit of it on a german web site complete with
component values and tolerances.

Does your machine date from around 1970? I had a high speed A77 from
around this time which used the discriminator. I still have the
service manual, but not the machine.


It's earlier. Judging from the serial number it is a MKII made in 1968. The
funny thing is, the manual I have describes the circuit operation as if it
were using the resonant circuit discriminator but the circuit diagram is of
the more modern version using a 555 timer.

Ian