Pioneer SX 626 distorted channel eliminated but...
I picked up this unit and started it with variac step by step.
After hooking up headphones, I noticed distortion in L channel. The sound as if the output transistors had been overdriven.
I gave a good spark of de-oxit around volume control, balance, selector switches and on/off rotary switch.
After dissassembling the unit and examining, I removed the output transistors, reapplied head-sink compound on each and re-soldered them each.
The distortion is GONE, but...
when I touched each and every transistor, the 'outer' transistor of the L channel was substantially hotter than the rest. Than I measured collector voltages and found that it's too high on 'outer' transistor. Supposed to be 29-sh Volts, but was near 45V! I tried to adjust it with VR1 pot, but was not successfull. I was only able to drop it by 4V down to max. The other channel I only moved pot a small notch to be exactly half of 'inner' transistor's collector.
I checked R15, R17 and R21 for proper values and these three are all fine and give good reading with small tolerance...
So far no culprit found, but have no desire to put together unit being not properly operating. I've also read about major overhaul which I'm not desire to do. Appreciate your help in advance!