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Old 07-11-2011, 04:24 PM
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bradman16 bradman16 is offline
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Pioneer SX 950 receiver output stopped, clicked, started again, now no sound.

Hi, I am sure there is a thread on here, but I can not find it. Can someone point me in the right direction please? I have a Pioneer SX 950 I have been using for years. Recently the sound would stop, the power transformed/output transformer? would "click" and reset. The power itself stayed on, but the sound stopped, then after the click, (similar to the one it makes when you turn it on), it returned to normal. But not today, all sound is gone. Powers on, no sound. What is the most likely culprit? Thanks so much guys.
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Old 07-11-2011, 06:40 PM
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first check the awr-101 board (power supply) voltages, especially the +35v power. That transistor Q5 is the first place to look, it is undersized and bakes to death when the ventilation around the unit is marginal.

of course before that download the service manual.

If you haven't done this before, tell us so we can add directions and precautions.

Quote:
AWR-101 board, these are regulated voltages, unless otherwise indicated. the voltage readings are ground referenced:
pins 2 & 3 +5.4v dc
pins 4 & 5 +13.9v dc
pins 6 & 7 +51.5 v dc
pins 8, 9 & 10 +36.5v dc
pin 11 +28v dc
pin 13 -13.5v dc
pin 14 -51.5v dc
pin 15 -19v dc
pin 17 - raw unregulated dc to the outputs,
pin 18 + raw unregulated dc to the outputs

AWM-062 protection board
pin 11 +36.5v dc
pin 2 -13.6v dc
pin 12 7.5v AC
pin 1 audio input, good would be dc millivolts, bad can go up to over 30v
pin 3 audio input, good would be dc millivolts, bad can go up to over 30v

copy these lines and add the readings you get at the end of each line. Easier to keep track of that way.
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Old 07-11-2011, 07:52 PM
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bradman16 bradman16 is offline
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OK, thanks for the tips, I have dabbled with electronics repair for 20 odd years, often when something like this happens I sell it for parts. However, this one is a keeper to me. I will post back when I find the solution. What you said makes sense, it was not particularly well ventilated, and I knew that, but I did it anyways, live and learn.
Thanks!
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Old 07-11-2011, 08:45 PM
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markthefixer markthefixer is offline
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Join Date: Apr 2005
Location: Bensenville,Illinois
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For success and my continued participation, please just post the voltages without tearing into anything.
That will determine the power supply's condition, and a parts list for remediation.
then we will see if we have to go further. to the protection, then the amps.

quite frankly there are a lot of 850/950 repair threads on here, and if you question why I mention the 850, you really need me.
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Old 02-17-2012, 10:20 PM
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JazzVinyl JazzVinyl is offline
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Quote:
Originally Posted by markthefixer View Post
first check the awr-101 board (power supply) voltages, especially the +35v power. That transistor Q5 is the first place to look, it is undersized and bakes to death when the ventilation around the unit is marginal.

of course before that download the service manual.

If you haven't done this before, tell us so we can add directions and precautions.
Sorry to revive an old thread guys. But my Pioneer SX-950 did exactly what the OP said his did. Cut out a couple times during play, but always came back alive. Last night, it cut out and did not come back.

When you turn it on, the relay never clicks and you get no sound.

Took the covers off and measured all the power supply pins as per this:

AWR-101 board, these are regulated voltages, unless otherwise indicated. the voltage readings are ground referenced:
pins 2 & 3 +5.4v dc
pins 4 & 5 +13.9v dc
pins 6 & 7 +51.5 v dc
pins 8, 9 & 10 +36.5v dc
pin 11 +28v dc
pin 13 -13.5v dc
pin 14 -51.5v dc
pin 15 -19v dc
pin 17 - raw unregulated dc to the outputs,
pin 18 + raw unregulated dc to the outputs

And all were very close.

Then I smelled a burn smell, and see that one of the IC regulators is way way hotter than the other and appears to be a bit burnt on one side.

I guess this is the problem.

Questions are:

1> Is it just the regulator, or does something upstream go bad and cause the regulator to fail?

2> This is the extent of my electronics knowledge. I will have it professionally repaired...any idea what an expected repair bill will be if it is "just the regulator"?

Appreciate VERY much!!!

.
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