I am looking for a service manual for this unit and some advice (common failures) for the audio issue.

I have no audio from the left channel, this is my fathers unit and he is the original owner, he has had it serviced once before for a similiar problem, looks like they replaced some resistors (not age correct).  Anyways I have taken apart the unit and found the paper envelope attached to this beautiful unit however it is empty.  I think that the previous repair shop removed it and anyways the secret papers are missing.  Can anyone confirm this was the service manual, or what was in this envelope inside the unit.

Thanks

Kris

The envelope should contain the circuit diagram. It is not the complete service manual. That is a rather more sizeable document! It is on site for silver and gold members. How useful it is depends a bit on how good you are at electronics! No use to me except that it tells you how to take it apart!

The envelope contained the schematics.

A missing channel could be caused by anything, capacitors, potentiometers, switch contact etc. Put an oscilloscope to the signal path to see where the channel is lost.

Martin