Pioneer SA-800 Tune Up

New components in place and all is good.

Except, now my Pioneer SA6700, that I am using to drive one set of speakers, stands out as being noisy. It is on both channels equally and it seems to be coming from the power amp section of that amp. I'll have to look into that...
 

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Found this thread and may try out some of your 'refurb' ideas... Here's a pic of mine:

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I'm bringing this thread back to life. Looks like TEN YEARS have elapsed since I started this thread. The amplifier distorted into 6 ohms but not into 8. Specs indicate it can handle 4ohm.

Turns out my notes here show I had set the bias to around 20mA, and this was just a guess by looking at service manuals of other Pioneer components that were similar.

Now fast-forward to today and it appears that the SERVICE MANUAL is now available on HiFi engine!

It seems that I have made the collector current too low. Looks like the manual wants 0.1V across the 1ohm resistors, giving 100mA. I have it set around 20mA.SA-800 BIAS.jpg
 
I opened the unit and wound up not doing the protection board calibration because it was not giving issues and to do it correctly it asks two twisted wires be removed from the protection board; there is no connector (Pins 2 and 4). They are asking DC balance to be measured at TP1 and TP2 with those two wires on pins 2 and 4 removed or connected to check the two sides which I did not do. I measured about 10mV on the RCA jacks on each side and left well enough alone on the DC balance.

On to the Idle Current.
RIGHT: The pot is very touchy and as I found it the voltage across the 1 ohm measured 2mV, or 0.002V when it should be 0.1V. So that is why that channel did not really work well. I cranked it up to 0.11V. I could not get exactly 0.1V because the pot was touchy.

LEFT: It read 0.025V but with the pot all the way over the best I could get was 0.05V so I left it there. Maybe someday I could look into that.

HOW DOES IT WORK NOW:
Best it has been ever, since I got it in 1980s.
 
LEFT: It read 0.025V but with the pot all the way over the best I could get was 0.05V so I left it there. Maybe someday I could look into that.
Some day is now. I have been noticing one channel weaker and sometimes distorting. So it is opened up again and I'm checking voltages and going back through ten-year old notes to see what has and has not been replaced.

I know for sure the electrolytic caps have not been replaced, so these are getting replaced (on order).
 
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