Soundcraftsmen PM860 red led light stuck on

[crooner2264]

Q7 keeps Q8 off. So voltage across R8 should shows there is voltage to turn Q7 on. Or check the base-emitter voltage of Q7.

That's good. Did you test the originals? I'm guessing Q2 was only functioning as a base-emitter junction. I match mine with a transistor tester. Otherwise you would have to build a test circuit to calculate gain. If all you have is a multimeter, you could match the base-emitter juction voltage with the diode checker function.

Hello, i am making an attempt to contact you about my pm860 amplifier. you seem to know these very well. i have been trying to repair a swapmeet find of a cosmetically good soundcraftsmen pm860. 1 channel is down and i have replaced all the semiconductors. with the mosfets removed i still get 69vdc on q7 transistor. any help would be appreciated thanks Frank