Hello my friends! I have a little problem with this amp and I'm wondering if anyone has had similar situation. I got this amp with both channels burnt out, so I changed all output transistors, their drivers and their respective resistors. Also some other transistors were shorted or just leaking and of course, both IC's PA0016 were out too. After I changed all of this, everything seemed to be ok. Without signal applied to input or with signal and volume pot turned up to 1/4 of total turn, it was ok. Output transistors and drivers becomes warm after very short time but temperature doesn't change or goes up. Quiescence current was about 200 mA. I don't know if it's ok because I don't have complete service manual, just schematic diagram. I noticed that output voltage is on one channel 2-4 mV but on the other it was constantly varying from 8-40 mV. Voltages on PA0016 were also as stated in schematic and stable. This second channel literally has burn out after I turned volume a bit higher than 1/4. Because those IC's PA0016 are pretty expensive, I checked once again the channel that remained alive, found nothing wrong and I've left it to play some more time to see what will happened. And it happened again. Just this time it was a bit later and at higher power (about 1/2).
Could it be because I didn't put inside exact original transistors but direct replacements ( for drivers and some transistors around PA0016, all of them in signal path or in power supply circuitry)? Does anybody know how is quiescence current adjusted on this amp? I guess PA0016 is in charge for this.
SO, it's a bit long one, but I'd like to fix this amp because I already invested some money in it and it looks pretty mighty. I hope it will sound up to its looks. :-)
Thanks in advance.
Best Regards, Livio