Lg 42pb4dt

[Phaihn]

original issue was turns on then makes a clicking sound and shuts off. replace most of the psu caps. no change till i unpluged some of the cables for the side boards first the ysus. tv would then turn on next i unpluged the other side while leaving the ysus hooked up got a spark at that and blew the fuse to the ysus now tv turns on.

can anyone give there input on if the fault was the ysus or something else?
thanks.

[Phaihn]

Re: Lg 42pb4dt

also what are the chances that this repair kit will work or am i better off replaceing the whole board?

http://www.ebay.com/itm/EBR36954501-...item255ebba0fd

[drpj23]

Re: Lg 42pb4dt

Generally with plasmas clicking off, it is detecting a short or issue with, and more than likely for you, the YSUS (well with LGs in this case - X-SUS or the P/S are common symptoms of this too). The fact the fuse blew kept the supply on means there is something wrong on that line.
(You can doubly confirm this by replacing the fuse - TV will click off - removing YSUS from power supply and it will stay on)

Also, I think you found a good reason why you should shut TV off and let the power supply discharge before (dis)connecting any cable ... especially those with a potential of 80-200V.

You probably didn't harm anything but as with any component repair, you may fix the power supply tripping off but still have issues. Though, LGs are notorious for the IPMs failing (and not blowing fuses too). The replacement also is a bit of a hassle (per other members here) but if the YSUS is around 100 and you feel confident then go ahead.

You should also verify voltages too just as a precautionary that everything is still stable and no other problems are existent.

[Phaihn]

Re: Lg 42pb4dt

i did shut off the set before unpluging stuff maybe i should of said that.
i think the issue was that when i unplugged the other board that all the power built up on the other side and sparked

[Phaihn]

Re: Lg 42pb4dt

from the looks of the lead on the above pics could that be from the spark i saw or could that be the couse of the fault? i think it was the psu that sparked but i am not sure.

[drpj23]

Re: Lg 42pb4dt

I can't see what pic you are referring to but sparking will cause a bit of discoloration and even eat away a little bit at the metal. (The arc-weld effect)
If you are concerned for the psu, just turn the set on again and check to see that the voltages are in spec and are stable.
And in reply to the previous message, the psu will hold a charge although the set is off and/or unplugged. Good to wait for discharge and you can check with a meter if there is still any potential on those wires. If you can't wait, you can use a resistor to bleed the charge off quicker. Use 5-50 Ohm/V and preferably a high wattage resistor.

[Phaihn]

Re: Lg 42pb4dt

I can't see what pic you are referring to but sparking will cause a bit of discoloration and even eat away a little bit at the metal. (The arc-weld effect)
If you are concerned for the psu, just turn the set on again and check to see that the voltages are in spec and are stable.
And in reply to the previous message, the psu will hold a charge although the set is off and/or unplugged. Good to wait for discharge and you can check with a meter if there is still any potential on those wires. If you can't wait, you can use a resistor to bleed the charge off quicker. Use 5-50 Ohm/V and preferably a high wattage resistor.

this one the crusty looking leed from the capacitor.

[Phaihn]

Re: Lg 42pb4dt

well anyway i cleaned it up i am going to try replacing the fuse and see what happens.

[drpj23]

Re: Lg 42pb4dt

That just looks like a bit of flux residue.
OK, post how it goes.

[Phaihn]

Re: Lg 42pb4dt

That just looks like a bit of flux residue.
OK, post how it goes.

i will after i go out and find a fuse.

[Phaihn]

Re: Lg 42pb4dt

ok same result turns on clicks off.

[drpj23]

Re: Lg 42pb4dt

And I presume if you remove the Y connector it stays on?
What do you get when you test resistance of Va and Vs to ground on YSUS? (With no voltage)

[Phaihn]

Re: Lg 42pb4dt

i have to remove the Y to test those right? and yeah i remove fuse and turns on. is the YSUS on the otherside?

[Phaihn]

Re: Lg 42pb4dt

no readings on Va and on Vs 001 on 2000 scale and 00.8 on 200 scale.

[drpj23]

Re: Lg 42pb4dt

You don't have to remove anything really but it may be easier to take the cable off as you did. The Y-SUS is on the left facing the back.
You took the resistance on those pins? There should be a mega-ohm setting you should start with first.

[Phaihn]

Re: Lg 42pb4dt

ok started with 20m didnt get much of a reading till i got to 200.

[Phaihn]

Re: Lg 42pb4dt

just got and installed the replacement part today tv is still clicking on and off anyone got any idea of what i should be looking at now or is it possible the replacement part is bad?

[Phaihn]

Re: Lg 42pb4dt

pic

[DigitalHandyMen]

Re: Lg 42pb4dt

Well I see this answer is very late, but here it is.

The problem with the TV is the power supply going into OCP(over current protection). The Transistors Q852 and Q851 are suffering from a C,B,E short. Basically the die has broken down and caused the Transistors to fail.
However this is not the entire problem. This issue was cause when IC U851 PN#L6598 High side driver became stuck on cooking the transistors.

Change the above parts and also change the 2 bypass diodes D851 and D852 PN# SB140. They are must likely compromised.

Best of luck!

Tim