willyrover
Super Member
If power supply voltages and relay coil voltages check out, I would start investigating the preamp - specifically what Yamaha schematic calls TONE CONTROL BOARD.
I'm looking at a CA-1010 schematic - but the 2010 is similar. The volume control is a somewhat complicated arrangement that, honestly, I've never really bothered to figure it out completely. The volume control has 4 potentiometers. Two are ahead of the tone board and two are after the tone board.
If the tone board is passing DC it MIGHT be increased or decreased by the volume control. (i.e., increasing the volume increases DC that is passed to the amplifier and triggers the protection circuit)
This is shotgunning it a bit, but at close to 40 years old, it's due. Check all solder connections on the tone board, replace all electrolytic capacitors, and replace VD1212 and HV46R "double diodes" with two 1N4148 diodes in series.
I'm looking at a CA-1010 schematic - but the 2010 is similar. The volume control is a somewhat complicated arrangement that, honestly, I've never really bothered to figure it out completely. The volume control has 4 potentiometers. Two are ahead of the tone board and two are after the tone board.
If the tone board is passing DC it MIGHT be increased or decreased by the volume control. (i.e., increasing the volume increases DC that is passed to the amplifier and triggers the protection circuit)
This is shotgunning it a bit, but at close to 40 years old, it's due. Check all solder connections on the tone board, replace all electrolytic capacitors, and replace VD1212 and HV46R "double diodes" with two 1N4148 diodes in series.