Hi all,
I have been working on this Pioneer SA-1000 on and off for a few weeks now with no luck.
One channel output was completely blown - Q15, Q17 (2SC1080) were both blown collector to emitter, R57 0.5 Ohm resistor on Q17 was blown open. Q9 2SC984 looks also shot at least through one junction.
So I originally replaced Q15, Q17 and R57 (Q9 stayed original). Turn it on, Q15 goes hot over ~10 seconds.
I shotgunned at that point and replaced every transistor as per consolidated list:
http://www.audiokarma.org/forums/index.php?threads/sa-1000-transistor-list.546251/#post-7155137
I also replaced the electrolytic caps on the board, and 2nd 0.5 Ohm resistor (R49).
Still have exactly the same problem.
I cannot adjust idle current at all through VR3 (I have 2A across those resistors in the bad channel).
All resistors are exactly the way they are supposed to be. Diodes and zeners measure ok. Capacitors are not shot through. I did not replace the variable resistors. VR1 definitely adjusts offset voltage.
I have not replaced VR3.
All power supply voltages are present. From measurements table, Pin to Pin 5 is 1-2V (depending on VR1 value), but not 0V (as in good channel).
I am also doubting why Q9 2SC984 is supposed to be replaced with KSC2383YTA, as current values for 2383 are three times higher than 984.
Any ideas are welcome. Thank you.
I have been working on this Pioneer SA-1000 on and off for a few weeks now with no luck.
One channel output was completely blown - Q15, Q17 (2SC1080) were both blown collector to emitter, R57 0.5 Ohm resistor on Q17 was blown open. Q9 2SC984 looks also shot at least through one junction.
So I originally replaced Q15, Q17 and R57 (Q9 stayed original). Turn it on, Q15 goes hot over ~10 seconds.
I shotgunned at that point and replaced every transistor as per consolidated list:
http://www.audiokarma.org/forums/index.php?threads/sa-1000-transistor-list.546251/#post-7155137
I also replaced the electrolytic caps on the board, and 2nd 0.5 Ohm resistor (R49).
Still have exactly the same problem.
I cannot adjust idle current at all through VR3 (I have 2A across those resistors in the bad channel).
All resistors are exactly the way they are supposed to be. Diodes and zeners measure ok. Capacitors are not shot through. I did not replace the variable resistors. VR1 definitely adjusts offset voltage.
I have not replaced VR3.
All power supply voltages are present. From measurements table, Pin to Pin 5 is 1-2V (depending on VR1 value), but not 0V (as in good channel).
I am also doubting why Q9 2SC984 is supposed to be replaced with KSC2383YTA, as current values for 2383 are three times higher than 984.
Any ideas are welcome. Thank you.