11-29-2017, 01:58 PM
(11-29-2017, 12:26 PM)jjmt Wrote: OK. Here's the thing. I don't know squat about solid state amplifiers, but I have something of a hobby in building and repairing tube amps. So, even though I feel quite clueless, I'm intrigued by just how on earth you could be getting 54 volts DC at the speaker. So I looked at this schematic.
If you go to the upper right hand side you'll see that there is 56.5 volts coming into the circuit. There are three paths down to the line that goes right to the speaker jack. On those three path is a diode (middle line, no idea why it is there) and two Q305's. The two Q305 take the 56.5 volts on the top, and then connect downward through what looks to be a 0.33 ohm resistor. You're supposed to see plus of minus 0.05 volts there. You get 54. So, either that diode has shorted (best case) or one of the Q305s has shorted (worst case, as I think those are the power transistors?). Anyway, you can test them. I googled up a thread here that might be useful, involving a multi-meter in diode mode.
Good luck!
Thanks! I was actually suspecting the power transistors and was going to replace them. I'll check out that diode as well. Thanks for the link. Should help a lot.