Pioneer sx-838 high dc in one channel

Tomcow

Active Member
Hello.I found a Pioneer sx-838 receiver at the junk that someone had thrown out.Some of the controls (volume,bass,and tuning knob broke.Repaired the controls,both a couple new knobs,cleaned it all up,recapped the power supply and tone boards and she looks and sounds awesome!One problem,right channel reads 0dc at the speaker terminal and 30mv dc offset.(excellent)Left channel 30mv dc offset but 250mv dc left channel output.Any ideas on possible problem?Thanks for any advice!Tom
 
Sorry.I meant bias,30mv,(idle current)and dc at the speaker terminals,right channel,0,left channel,250mv.Thanks.
 
Your description doesnt detail if you have tried adjusting the bias - using the process in the service manual?
 
Yes.What could be the problem when the receiver will relay on (lights dim and hear two clicks,but won’t relay on when plugged into wall outlet?
 
Ok.Did some more diagnostics on my Pioneer SX-838 receiver and came up with some interesting readings.On the power supply board,pin 7 supposed to be 45V,Got 44.2.pin 9,supposed to be 13V,got 157mv! Pin 13,supposed to be 35V,got 14.8V.Pins 14 and 21,12.5 and 8.5V,got 12.7V and 7.3V The protection board,pin 1 supposed to read around 1mv,got 10V! Pin 2,13mv,I got 157mv,pin 3supposed to be 75 mv,I measured 13V,pins 10 and 11 both supposed to read 35V,I got 14.8V on both.Pin 12 is ac,supposed to read 7.5 V,I got exactly 7.5V.I can’t figure out where the problem might be.Amp board readings are all good but the emitters on the left channel are reading almost 3volts.The right channel emitters are at 16mv and 55mv.Tom.
 
Ok.Did some more diagnostics on my Pioneer SX-838 receiver and came up with some interesting readings.On the power supply board,pin 7 supposed to be 45V,Got 44.2.pin 9,supposed to be 13V,got 157mv! Pin 13,supposed to be 35V,got 14.8V.Pins 14 and 21,12.5 and 8.5V,got 12.7V and 7.3V The protection board,pin 1 supposed to read around 1mv,got 10V! Pin 2,13mv,I got 157mv,pin 3supposed to be 75 mv,I measured 13V,pins 10 and 11 both supposed to read 35V,I got 14.8V on both.Pin 12 is ac,supposed to read 7.5 V,I got exactly 7.5V.I can’t figure out where the problem might be.Amp board readings are all good but the emitters on the left channel are reading almost 3volts.The right channel emitters are at 16mv and 55mv.Tom.
Be a lot easier to read if you listed pins ... and correct polarity.
Pins..
7 -45....44.2
9 -13 ... 157mv
etc...

You need to get the power supply squared away first.. Then press on to the protect board.
 
I’ve pretty much rebuilt the entire power supply.Capacitors,transistors,diodes,can’t figure it out. I’m missing something somewhere.Protection board again:pin 1,plus 10V(dc) pin2,minus 156mv,pin 3,-12.8V,pin 4,0mv,pin5,plus 10V,pin 6,plus 10V,pins 7 and 8,minus12.9V,pin 9,plus3.8V,pins10 and 11,plus14.7V,pin12,7.4V(ac) Power supply board.pin 1,minus 21mv,pin 2,plus 20mv,pin3,plus 20mv,pin 4,plus 41.2V,pin 5,minus 41.3V,pin 6,0mv,pin7,minus 43V,pin 8,minus 153mv,pin 9,minus 155mv,pins 10 and 11,plus 10V,pins 12 and 13,plus 14V,pins 15 and 16,0mv,pin 17,plus 49V,pins 18 and 19,minus 187mv,pin 20,0mv,pin 21,7V,pin 22,6mv,pin 23,plus 6.2mv,and pin 24,minus 6.2mv........whew!!!!!Any thoughts are welcome!Tom.
 
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