Unfortunately, I don't have a scan of this schematic. What the failure
most likely means is that the protection circuit IS working, and you
have a bad amplifier channel. Look for DC voltage on the emitters of
the output transistors. One channel will probably be near 0, and the
other will have quite a bit of + or - DC on it., which is what the relay
is there for. It is less likely though possible that the protection
circuit itself has developed a fault.
> I need a schematic for a Yamaha R-900 Receiver.
> The protective circuit relay has stopped engaging.
> Any advice or assistance is appreciated.
<email@example.com> wrote in message
> Hi Tim,
> Thank you for your reply.
> I have not had a chance to check the Yamaha, however I do have a
> Marantz 2330B that has DC Voltage in one channel.
> So, from a novice, what would dc voltage indicate?
If it's the full rail voltage, could be a bad transistor, preamp transistor
pair, bad resistor, bad cap.
Intermediate voltage I'd lean more to a bad cap (feedback circuit)