Crown Micro-Tech 2400

[xtian]

Crown Micro-Tech 2400 on the bench, one channel working and one not (nice, because I can compare!). On bad channel, signal vanishes as shown on schematic snip attached, where red X marked. On good amp, signal is strong at that location. So, the op-amp U204 is working, but something after resistor R203 is pulling the signal to ground. (R203 measures OK). What can I look at next?

[The Dude]

The schematic is incomplete, so I can't say this with any certainty. I believe that where you have the red X is feedback from further down the line. Your problem is more likely in the final output section. I've worked on lots of these and almost any time one goes down, it's because output transistors are shorted. I would start by checking those.

[xtian]

I also posted the complete schematic--it's the PDF in post #1.

There's no call to check the power amp, because the signal never exits the preamp board. I need to solve this problem first.

There's a whole error checking, muting section of the schematic that is suspect, but I don't understand it's function or how to check it out.

[xtian]

Anyone willing to look at this?