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Hello all
This one is doing my head in
It came in dead. Blown fuse replaced fuse and under Lamp limiter i can see excess current draw.
Removed the power leads to Power amp and found one channel is the cause.
with the bad channel disconnected all working correctly on the other channel
Located a s/c bridge replaced tested still the same
I saw a couple of the 0.22R 5watt to be ok but dis coloured, where the others were not.
So as i have all the transistors in stock i decided to to blanket change of them
4 x 2sc5200
4 x 2sa1943
2 x 2sa1837
2x 2sc4793
All like for like and all new
on start up excess current draw through the lamp limiter , then i spotted it The triac on speaker board was short
Could of kicked myself , anyway replaced it , with no speaker load, there is 90+v on speaker out with no excess current draw
These are difficult to work on at the best of times, so before i removed the transformer so i can test on the bench and work on it easier So i have gone over the board trying to do some cold checks comparing working to non working
I have found nothing,
Im not so hot on the ss amps. sadly ....
But i have found one thing which i think is nothing but i would like to ask
when i use the DMM on the output transistors i have different reading from
Base to emitter on Q220 -Q219 23 ohms ( R279 and R403 ) ( 47R ok
Base to emitter on Q120 -Q119 6 ohms ( working channel )
I have checked all 0.22r and all diodes and other semi's that can be tested
all the other reading from channel to channel are the same
LT +/- Rails are there
Ht + /- are present
peavey_xr8600_sch.pdfany help on this would be grateful
This one is doing my head in
It came in dead. Blown fuse replaced fuse and under Lamp limiter i can see excess current draw.
Removed the power leads to Power amp and found one channel is the cause.
with the bad channel disconnected all working correctly on the other channel
Located a s/c bridge replaced tested still the same
I saw a couple of the 0.22R 5watt to be ok but dis coloured, where the others were not.
So as i have all the transistors in stock i decided to to blanket change of them
4 x 2sc5200
4 x 2sa1943
2 x 2sa1837
2x 2sc4793
All like for like and all new
on start up excess current draw through the lamp limiter , then i spotted it The triac on speaker board was short
Could of kicked myself , anyway replaced it , with no speaker load, there is 90+v on speaker out with no excess current draw
These are difficult to work on at the best of times, so before i removed the transformer so i can test on the bench and work on it easier So i have gone over the board trying to do some cold checks comparing working to non working
I have found nothing,
Im not so hot on the ss amps. sadly ....
But i have found one thing which i think is nothing but i would like to askwhen i use the DMM on the output transistors i have different reading from
Base to emitter on Q220 -Q219 23 ohms ( R279 and R403 ) ( 47R ok
Base to emitter on Q120 -Q119 6 ohms ( working channel )
I have checked all 0.22r and all diodes and other semi's that can be tested
all the other reading from channel to channel are the same
LT +/- Rails are there
Ht + /- are present
peavey_xr8600_sch.pdfany help on this would be grateful
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