OK, the Q4 was OK
seems both channel component are ok and the circuits are working, except below condition which make it output DC
seems both channel component are ok and the circuits are working, except below condition which make it output DC
I have no idea at this moment, sorry
In relation to your report in message #49 and my response on it, please check the marked trace carefully.
Q9...............OPEN CIRCUIT GOOD BOARD .... THE READING IS FROM THE BASE TO COLLECTOR...........ALSO Q9 IS A BRAND NEW TRANSISTOR IN THE BAD BOARD.
Last edited:
You have the boards on hand, If you think Q9 maybe bad, you may try exchange them, if no change you can put it back
i have changed that Q9 already several times, it is not Q9 but what ever else is connected to it
Below is just my thought, you decide ok or not
borrow one capacitor C2 470p from the other totally bad board
solder the capacitor directly to Q9 pins base and collector in the PCB layout side
if no change you can put it back
where does the voltage come from all pins of Q9 66vdc high voltage. .the collector goes to the pos rail, i understand, but base? where the high dc volt come from
The pictures show you are using component measuring where it is expected that you use voltage measuring of a powered-up amp. That's why you get all these weird readings. In circuit measuring of components using a DMM is not of much use.
I have tried it both ways. with the amplifier on and out of circuit. I have compared it to another amplifier of the same make model .the working amplifier does not have Q9 base to ground 66vdc and emitter to ground 66vdc also.
I have pulled every semiconducter and tested it with a dvom and an advanced tester. I even installed all new parts and still cant figure out why i have the high voltage.I pulled the little pf caps thinking maybe they were bad causing occilation but my capacitor tester does not do a good job of measuring them.