Hi sorry for long term response. Im in the middle of Christmas preparation. . We need to know where the supposed 12v to pin 15 drops, btw i think the amp worth the effort. Those classic amplifiers deserve a second chance.
Absolutely no problem! Thank you for helping with this - take your time. There is no hurry-
Tracing things from the remote power in with 13v where enters the board. It goes through a 100kQ resistor, afterwards there is .003v into the base of a small transistor. following the board labeling, there is also .003 on the emitter, and 6v to the collector. It goes through few more resistors, and I have not been able to trace things much further - now its in the black area from the old blown transistor. Pretty sure it ends up on the formerly blown transistor.
Tracing pin 15 back, it goes to the middle leg (collector) of the transistor I replaced. There is 13v to the other leg, and the 6 volts on the other.
If I remove the remote power, there is still .002 all through the remote power circuit - its like the remote power doesn't really do anything, unless it is switching on a .001v difference.
Did I pick a bad substitute for that D600K? Could it have been something other than a D600K?
thanks-
Tracing things from the remote power in with 13v where enters the board. It goes through a 100kQ resistor, afterwards there is .003v into the base of a small transistor. following the board labeling, there is also .003 on the emitter, and 6v to the collector. It goes through few more resistors, and I have not been able to trace things much further - now its in the black area from the old blown transistor. Pretty sure it ends up on the formerly blown transistor.
Tracing pin 15 back, it goes to the middle leg (collector) of the transistor I replaced. There is 13v to the other leg, and the 6 volts on the other.
If I remove the remote power, there is still .002 all through the remote power circuit - its like the remote power doesn't really do anything, unless it is switching on a .001v difference.
Did I pick a bad substitute for that D600K? Could it have been something other than a D600K?
thanks-
ok, with this info assume there is something wrong, Pin 15 can't go to collector of NPN D600k, doesn't make any sense. But if the fried transistor was PNP like 2SB631 the circuit could work, explanation on NPN D600k collector (middle pin) must have +Vcc in this case +12V from batt , emitter should goes to pin 15, but seems we have the upside down, IF the info you gather is correct, it should be a PNP ( 2SB631) emitter goes to 12V and collector goes to pin 15 accorded to your data.
I know its really old thread but maybe it will help someone. I bought a Volvo 780 with same non working rear amp. Same transistor burnt as mentioned here but mine was still readable. It is PNP indeed and B631k just as mentioned. So I replaced the transistor and 2 5600uF and 1 4700uF capacitors and gotnit working again. I think the big capacitors had shorted over time and burnt the trans.
Hope it will help someone 🙂
Hope it will help someone 🙂