Dear all, again i am in this condition, i sold the old SA-8800 and bought a new one, and for the second time i have the same problem. I was not able to solve it the first time, hope someone this time can help me. The unit was quite noisy on inputs so i put it on the bench and saw some troubles of noise and spikes on power supply, then at about 15w power the negative part of the sine waveform start to clip if i add more power at about 20 w the protection shut it off. I was able to recap and change some transitors on the input section and power supply, now the power is steady, nice and clean and the pre do its job as it should. The problem left is the Power amplifier. I make all adjustments described in the manual succesfully. the only thing that i can find not in line with the scheme is the voltage on emitter of Q13 i have -26 volts instead of -46 i check q13 and q17 they are good, how can i test the zener d1 and d3? anyone can help debug this fault? thanks, i attach the Scheme
Attachments
Is the -48 volt rail correct on Q13 collector?
The Zeners are for protection only to limit the voltage seen between the two inputs (inverting and non inverting) of the power amp. You can remove them as a test but I doubt they will be faulty.
Is the fault on one or both channels?
The Zeners are for protection only to limit the voltage seen between the two inputs (inverting and non inverting) of the power amp. You can remove them as a test but I doubt they will be faulty.
Is the fault on one or both channels?