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LG HT33S

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blackillusion:
Im stuck for ideas, I desolder and tested optocouplers. Check resistors, check diodes, check IC's, check transistors. Everything I tested seems okay.

Im missing some voltages on secondary side. ICs not output voltage, big diode test ok. I'm trying to learn and won't give up, just keep coming back to it.

blackillusion:
Ok so I must apologize for wasting some time. I found that a ribbon was not connected properly on other unit. Now back to the high pitch sound

http://youtu.be/ryxeJLIIbaY

It comes from the PWM board.

tv tony:
Right, you sound to be going round in circles here, at least you have the machine powering up again. First of all tell me if the high pitched noise varies with the volume being adjusted, and is the noise you mention actually coming from the sub woofer drive unit or from components within the sub enclosure, by the way we are LG!

blackillusion:
hi tony thanks for the reply. I have since located a voltage regulator on the power supply that is meant to be a 3.3v and someone had put a  5v reg in there. It supplies the PWM so i'm guessing thats why its making that noise. Just waiting for replacement parts.

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