This is a 5-channel amp, looks a bit I think like the REF475. The 5th channel is Class AB and has a problem in this amp. If I remove the rectifiers from the PS for the sub channel the amp will power and probably work on Ch1-4 which is using TIP35C/36C for outputs
Putting the sub channel rectifiers back in, the amp cycles on/off repeatedly while drawing about 3A every ~4 seconds. I'm observing variating -5vDC to +14vDC on the sub channel which is using 2SC4468 and 2SA1695. None of the output BJTs are shorted. Rail voltage appears to be up to +-42vDC.
Whats the best way to disable protection in this amp to help locate the issue?
Putting the sub channel rectifiers back in, the amp cycles on/off repeatedly while drawing about 3A every ~4 seconds. I'm observing variating -5vDC to +14vDC on the sub channel which is using 2SC4468 and 2SA1695. None of the output BJTs are shorted. Rail voltage appears to be up to +-42vDC.
Whats the best way to disable protection in this amp to help locate the issue?
Actually I think I figured this one out, but could stilll use a suggestion.
The negative voltage regulator at D20, 2SA940; was not outputting -15vDC. Replaced it with some broke-down parts and now all opamps have +-15vDC. Amp says powered on.
Can I replace 2SA940 with 2N6491 as a -15v regulator? This part is synced and just below the large rail caps in photo.
The negative voltage regulator at D20, 2SA940; was not outputting -15vDC. Replaced it with some broke-down parts and now all opamps have +-15vDC. Amp says powered on.
Can I replace 2SA940 with 2N6491 as a -15v regulator? This part is synced and just below the large rail caps in photo.
Either should work. With 63 v rail caps, the voltage they will see shouldn't be near the rated voltage of the transistors.
I went with MJE15031G as it has a higher voltage rating. It worked just fine.
This amp is fixed, but I want to mention that this amp was having trouble under load with my scope probe attached to bridging speaker terminals referencing non-bridging terminals. Every time the amp pulled 8A of current, it would shut down. I had to flip my probe to 10X and amp passed full load out to clipping. My OScope was loading something.
This amp is fixed, but I want to mention that this amp was having trouble under load with my scope probe attached to bridging speaker terminals referencing non-bridging terminals. Every time the amp pulled 8A of current, it would shut down. I had to flip my probe to 10X and amp passed full load out to clipping. My OScope was loading something.