"N_Cook" wrote in message
...
No R speaker nor R line out, L &R phones out seem ok, as does the speakers
on/off sw. Amp hiss from the R speaker only, L is fine.
I got inside this 7 octave thing without breaking any foil ribbons. The
phones input socket switches seem ok, so does the line out sockets. But
the
Line-In Left/ Mono input has a bad bypass switch. Although it is in a
position that would suggest a Ring contact it seems to be a tip contact
switch, difficult to trace the local traces as vias etc.
Anyone know if the problem there would cause the loss of one channel. As
difficult to "bench test" this sort of item, any other areas to look at
before some sort of reassembly?



The line outs, phones and power amp are all sourced from the same pair of
signals, so if the phones work, the problem is from IC1 onwards to the IC3
power amplifier with regards the speakers, and there is a separate fault
with the line out. Probably.

Incidentally, there are just two dual op-amps between line ins and line
outs, plus a couple of mute transistors at the line out sockets, so this
should be trivial to troubleshoot as it doesn't involve the rest of the
keyboard at all.


I have the schematic on pdf I can email you, it is 6.4MB.



Cheers,


Gareth.