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Pioneer SX-535 with blown fuses F7 and F8

You are now in the "lazy mode" as you operate the amp without all four output transistors, right? I'm losing track of the voltages on the various electrodes of the bad channel. The pic above isn't all to clear but it seems that the input stage also has bad voltages. What is the voltage on the speaker connection pin#7? And what are the voltages on Q10?
 
Yes, without all four output transistors.

AWH-035 Pin 7 = -0.11V

Q8 base = +1.2V

Q10
base = -1.44V
collector = -26.5v
emitter = -0.82V
 
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Me thinks it is time for a reset. I'm having trouble figuring out where things stand so I'm going to back away from this one and watch for a while. :lurk:
Plenty of others to assist.
 
So Q12 and Q14 out of circuit and 110mv DC on right channel output pin 7? This started with bad outputs being replaced with the wrong types (NPN with PNP etc.)?
 
I would not. The bias is way too high. First get the bias voltage down from 2.64 to 2.40 or even less. Then fix the large offset of 0.11 V on the speaker terminal. Has something to do with the input stage. Maybe replace both transistors there. 2SA970 is a good replacement. Dunno if 2SA726 is failure-prone. Maybe C16 (wrongly referred to as R16) is bad. Once bias and offset are OK the outputs can be put back in.
 
PE9ZZ said:
I would not. The bias is way too high. First get the bias voltage down from 2.64 to 2.40 or even less. Then fix the large offset of 0.11 V on the speaker terminal. Has something to do with the input stage. Maybe replace both transistors there. 2SA970 is a good replacement. Dunno if 2SA726 is failure-prone. Maybe C16 (wrongly referred to as R16) is bad. Once bias and offset are OK the outputs can be put back in.
Click to expand...
2SA726 is most definitely failure prone.
 
Thank you to everyone who helped me with advice and made it possible for my Pioneer to work again. The problem was a wrongly installed Q8 and fake reprinted KSB596YTU transistors (Q13–Q14). Since this was my first repair of an audio device, I wasn’t very confident dealing with the voltages on the AWH-035. Now everything is much clearer… the receiver sounds great!

sx535.jpg
 
prenex said:
Thank you to everyone who helped me with advice and made it possible for my Pioneer to work again. The problem was a wrongly installed Q8 and fake reprinted KSB596YTU transistors (Q13–Q14). Since this was my first repair of an audio device, I wasn’t very confident dealing with the voltages on the AWH-035. Now everything is much clearer… the receiver sounds great!
Click to expand...
I assume you got the bias set without issue?
 
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