Author Topic: LG 42 PN4500 abnormal picture  (Read 282 times)

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P.R.Gore

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LG 42 PN4500 abnormal picture
« on: August 16, 2017,07:41:28 »
Hi,
LG plasma tv ; model number 42PN4500 is showing picture with enormous number of black spots or say patches. All voltages that mentioned on panel steaker seem normal.(Vsus & Vad ). Please observe attached photos & suggest solution.
Regards
P R Gore

Mulja tv repair portal

LG 42 PN4500 abnormal picture
« on: August 16, 2017,07:41:28 »

downunder

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Re: LG 42 PN4500 abnormal picture
« Reply #1 on: August 16, 2017,20:36:00 »

Looks like a faulty Z-Sus to me.

You could disconnect the flexi from the main board to the control board (under the PSU). At probably around 4 o'clock position on the big chip on the control, you should find the auto gen test points - could be marked R51/R52. Short these out and check the test patterns. If OK, main board is faulty.
If not, probably Z-Sus.                       Bruce

P.R.Gore

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Re: LG 42 PN4500 abnormal picture
« Reply #2 on: August 17, 2017,03:44:24 »
 Bruce,
As per your suggestion I connected jumper, the same fault appears in test pattern also. So fault should be in Zsus board. Can Zsus be repaired at component level ? Any repair hint?
Thank you very much for this repair suggestion! Waiting for your further reply.
P R Gore.

Mulja tv repair portal

Re: LG 42 PN4500 abnormal picture
« Reply #2 on: August 17, 2017,03:44:24 »

downunder

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Re: LG 42 PN4500 abnormal picture
« Reply #3 on: August 17, 2017,04:18:44 »

 No specifics, just to check FETs and Diodes for shorts and dry joints.     - Bruce

P.R.Gore

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Re: LG 42 PN4500 abnormal picture
« Reply #4 on: August 17, 2017,08:01:19 »
Ok. I will check & update.
Thanks.

tv tony

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Re: LG 42 PN4500 abnormal picture
« Reply #5 on: August 17, 2017,09:49:56 »
Doesn't quite look Z-sus to me. Hard to tell from camera shots but it looks to have plenty of brightness to it.
Spell checked unlike some posts.

Mulja tv repair portal

Re: LG 42 PN4500 abnormal picture
« Reply #5 on: August 17, 2017,09:49:56 »

P.R.Gore

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Re: LG 42 PN4500 abnormal picture
« Reply #6 on: August 22, 2017,14:56:03 »
I throughly checked Zsus board but could not find any def
ective igbt or fet,I also I tried by replacment of electrolytic
Capacitors. But problem remains same.

downunder

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Re: LG 42 PN4500 abnormal picture
« Reply #7 on: August 23, 2017,05:15:03 »

Might be time to move to the Y-SUS. Do Vs and Va match the values printed on the panel label?

On the Y-SUS check D515 and fuse FS501, and resolder the adjacent transformer.                                Bruce

P.R.Gore

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Re: LG 42 PN4500 abnormal picture
« Reply #8 on: November 20, 2017,10:58:00 »
Thanks Bruce,
This set is still pending at my workshop, I will check as per your suggestion & revert.
P R Gore

 

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