Pioneer SX-8 no fm or am

Is there and possible way it could still be in tc/power supply gwm 229 , I have also checked main output trans and thought left giant heat sink fins were warmer than right . I’m missing something
 
supereagle said:
PE9ZZ I keep going over the boards testing , any ideas of what could be the cause for it clipping
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You haven't defined "clipping". It is what it should do if you try to exceed the power rail voltages. Yours are +/-50 V under load so clipping should occur at +/- 45 V or so.
 

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PE9ZZ it will kick the relay out so I guess it goes into protection mode , I’m not gonna make a habit running it hard I just want to get that problem fixed before it gets worse
 
supereagle said:
PE9ZZ it will kick the relay out so I guess it goes into protection mode
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That means that there is an issue with the speaker protection or you really do get DC on the output. I dunno the English equivalent for the Dutch meten=weten (test is best?) but you must confirm by actually hooking up a multimeter to the speaker output(s). If you turn it up and it conks out without any DC your prot cap C139 has gone phut.
 
PE9ZZ I did exactly like you said no dc and cut out , pulled amp board pulled C139. 470uf 6.3v it measured 376.2uf replace with 470uf 16v also pulled C140 100uf 25v 86.2uf . There are 2 More caps 0.22 50v should I replace those they say non polar but it does have positive sign on board , I have 0.22 50v caps but they are not non polar
 
supereagle said:
still does the cuttting out at 21-22
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It makes no sense. C139 is OK so replacement was unnecessary. Studied the schematic some more. The other caps you replaced, C129 and C130, are in the overload protect circuit. They are innocent as well. When Q125 or -6 conduct due to overload in R186 they make Q139 conduct which pulls C140 to ground. This will cut out RL1. Does it cut out on headphone only? Or on different speakers?
 
I don’t have anything hooked up when I turn it up Speaker switches are kicked off and headphones unplugged, i can adjust idle perfectly, but can’t adjust speaker dc
 
supereagle said:
i can adjust idle perfectly, but can’t adjust speaker dc
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That is weird. VR1&2 are DC offset, VR3&4 bias. What is DC output voltage on your speaker terminals when it cuts out? You have no load connected then? I have a hard time understanding what is happening at your end...
 
So main outputs 2sa1216 87 degrees 2sc2922 84degrees this is tight side Left side is 2sa1216 67 degrees 2sc2922 is 69 degrees I tested with heat laser gun after 20 minutes of running
 
So I checked mains q1 q2 q3 q4 Q1 at C should be -50-55 I have +59.49. Q3 should be +50-55 on B . C should be 0.6 . I have +58.9v at C and 0.849 at B
 
supereagle said:
The readings on q1-4 I measured but the manual almost doesn’t make sense
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The manual makes perfect sense. You are measuring the output transistors. Q1 and Q2 (2SC2922) have the positive rail on their collectors, Q3 and Q4 (2SA1216) the negative. Q1 and Q2 base should be +0.6 V, Q3&4 -0.6 V. This is exactly what the manual says. If your output transistors run hot without any signal or load your bias is waaaaaaaaay too high. There are two bias adjustments for each channel. Never seen it done like this before. Dunno how they interact but it seems that you start with them both fully counterclockwise, turn up VR3(4) to get 56 mV then VR5(6) to increase it to 70 mV (JP1-JP2/JP4-JP3). The output transistors should stay cool at this value.

Oh, BTW, your degrees are in Celcius or Fahrenheit? If the latter temps are fine... :rflmao:
 
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