[Amps] Help - Alpha 91b

[David Jones]

Need help with ailing 91b (for a friend actually).
Amp tripped offline (protection circuit he thinks) over a year and a half
ago.  In the space of time since he has been trying quite hard to get some
concrete answers to what might have gone wrong.  No apparent smoke let out?
Simply puzzling.  Not sure where to start...

Has anyone:
1) Actual schematic of the 91b (the Russian made)?
2) Actual setup and test procedures for re-alignment after any work?

Friend has credentials to work on the amp!  It's simply not an option to
send it down to Colorado ($$$) to get it looked at and fix.  Just a look
would be hundreds of Canadian dollars (which are in better shape than they
were against US, but it's still brutal).  Fixing the thing would be half the
price of the amp when done (or more).

Help please?

David VE3STT
djones449 at cogeco.ca