Riddled TV Repair Forum

sdcovington · Joined: 10 Dec 2008 Posts: 3 Location: Fort Worth TX

Our LG 42PX12X made a loud popping sound yesterday morning, then the picture is gone... no TV menu, nothing. We can hear audio and change channels but no picture whatsoever.

After reading some other posts, it sounds like a Ysus, Xsus, control board, etc... I'm a layman to TV repair but I'm opening it tonight to see what I can find. I've built/repaired PC's so I'm hoping I can hold my own in the TV repair world :)

1) What should I look for to tell which board went out?

2) Where are the boards located to know which is which?

3) Do you have any suggestions on which would most likely be the issue?

Thanks so much for any help you can provide...

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sdcovington · Joined: 10 Dec 2008 Posts: 3 Location: Fort Worth TX

In looking at the service manual, it sounds like if there's no picture at all it's the control board that is bad... can someone verify this? PLEASE HELP! Thanks

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

It is not a good idea to guess as all it usually does is cost you money.

That being said. Do this.

On the power supply pcb. (this is the large board with all of the transformers, very large capacitors usually found in the middle top of the chassis) on the left sedge there will be a large connectors (P8011) with printing on the board indicating what is supposed to be on the individual pins. They will be VS, VY, VA etc. The voltage range will be anywhere from -200VDC to +200 VDC and what the level is supposed to be will be printed on a sticker that is on the panel itself.
After you find the connector P8011, if any of the voltages is low or missing, turn the set off and unplug the other end of the connector. turn on the set and see if the voltages come back.

Here is the summary of it.

Problem: No video, sound ok.
Solution: Check -VY voltage. If low or missing, replace the upper and lower Y drives and the Y-Sustain PCB. If the -VY voltage is ok, jumper pins 1 & 2 of P1 connector on the CTRL PCB. If test patterns appear, replace the main digital PCB. If bad or no test patterns, replace upper and lower Y drives, Y-SUS and Z-SUS PCB

If you do this be carefull as - + 200 volts Hurrrts and if you slip you can do more damage.

Hope this helps

Jesse

sdcovington · Joined: 10 Dec 2008 Posts: 3 Location: Fort Worth TX

Thanks so much Jesse... I took it to a repair shop and they diagnosed it as a YSus board problem. They want $600 to replace it so I'm considering doing it myself.

Do I understand you correctly that replacing only the YSus board without replacing the upper/lower drives is not a complete repair?

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

About 60% of the time the Upper and Lower buffers have failed causing a cascade reaction the takes out the YSUS pcb. If you replace the YSUS pcb and the Upper or Lower Buffers have failed there is a possibility that the shorted buffers will damage the new board. By Examination of the Buffer boards you can sometimes see a physical damage problem on the Ic's if they do not have heat sinks on them. It will look like a small hole blown into one of the Ic's. If you replace the YSUS pcb and turn it on, if the boards have failed and the YSUS board does not emediately refail there will be horizontal black lines on the upper or lower half of the screen or even both halves.

All that being said, the price quoted is a very fair price as the board is usually expensive and it sounds as if the labor portion is reasonable. The only question I would have is "What if it does not repair the problem??" to be put to the Servicer.

Hope this helps

Jesse

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