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LG 42pc1dv picture gone

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oggy:
Hi. Picture gone on an LG 42pc1dv-ec plasma. Sound OK, inputs OK.
Vs fuse blown on y-sus board. Replaced it but still no pic.

Checked voltages from PSU when switched on from cold.
Vs>300v Va>80v. Label says they should be Vs=185 and Va=60.
Noticed voltages slowly dropped to about their correct levels after 20 mins.
Is this normal as the set warms up ?

Read that the y-sus can give problems on these models.
The replaced fuse has not blown again so now I am confused (no pun intended)!
Only a novice so any help appreciated. Thanks.

brainstorm:
Hi Oggy,

I had one of these models  last week with one of the fuses blown but it displayed a very poor picture,
I didnt try replacing the fuse because it was reading 15 ohms to earth.
I replaced the board and the set worked fine.

Hope this helps

Brian

oggy:
Hi Brian, thanks for the reply.
It's just that I'm trying to rule out the PSU before I go for the y-sus. Don't want to spend over £100 for a ysus and find its the PSU !!
Regards, Malc

norman:
Hi Malc, I have just repaired one of these, the y sustain board was faulty. If the VA & VS voltages take about twenty minutes to come down then I suggest you have a psu fault as well. It may be the high voltages has damaged the y sus board. Try heating and freezing capacitors in the psu to see if there are any substantial change in VA & VS voltages. Hope this helps you, Norman

oggy:
Hi Norman. I've solved the high voltage problem.
It was a faulty digital multimeter and now all the PSU
voltages check out OK, as well as the -Vy and Vsc on the
Y-sus board.

One time when I was swithching the set on I noticed a spark
come from one of the FET's on the small heatsink on the Y-sus.
Read from LG training manual on the net that these can fail.

Has any body tried checking and replacing these 5 FET's and
got the picture working again ?
Also noticed the large heatsink on Y-sus is not getting warm,
like the others. Don't Know what's underneath it but guess
that's not working too !

Thanks for the help,
Malc.

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