LG 42PX5D - Clicking repeatedly

[tom66]

Just got this one in... am hoping it has the same cause as the LG 42PC1D I recently repaired, as the symptoms are identical. When plugged in, two clicks are heard, and a few seconds later the screen flickers (just a flash or two), then it clicks off. And the cycle repeats.

The fix involves replacing 11 capacitors (9 x 3300u 10V, 1 x 1000u 10V, 1 x 680u 50V), and disabling the AC detect. I already have the caps as spares.

Will post tomorrow when I get to open it up...

[tom66]

Re: LG 42PX5D - Clicking repeatedly

Okay - First impressions.

The symptoms -aren't- identical and it's actually got a nice Sanken power supply with good Chemicon caps in it.

When I plugged it in & turned it on:
- power LED came on
- after a couple of seconds a buzzing sound is heard and the screen starts filling in from the edges
- the TV then shuts down and needs to be unplugged for about 20 seconds before this can be re-attempted.

Sounds like a Z-sustain fault and most likely a fuse issue for the Va line, not the actual IPM, but the IPM is pretty cheap anyway. (Just not had the misfortune of trying to remove or install one yet.)

BUT, I then took the cover off -

It's FULL of dust. It's one of the earlier LG plasmas that has a fan for cooling the Y sustain board, and the entire area is coated in thick dust.

Powered it up again and a very loud buzzing was heard then BANG one of the diodes on the sustain blows up with a nice yellow spark and some smoke and the TV shuts down. Later saw it was coated in some kind of thick dust, but it looks like the diode has had its time.

The cooling fan does not appear to be spinning so it could be shutting down because of that.

More debugging to follow.

[tom66]

Re: LG 42PX5D - Clicking repeatedly

Okay, tested the fan with a battery - dead.

Cleaned out the dust. Must be cigarette dust - smells awful. Kind of like an old bar. Maybe it was used in a bar? Tested fan again, and it now spins. So that's fixed.

Next step was to deal with the diode - actually it is a MOSFET - cleaned off the dust and tested it, looks like it somehow survived . Plugged it in and the picture looks really bad, but it's there. Full of sparklies and taking ages to fill in, classic Z-sustain problem... or is it?

Vs voltage measured 1.5V over rating (196.5V vs. 195V), adjusted that down to within 0.1V and picture is far better now - still full of sparklies but looking pretty good, and no problems with fill in.

Not bad for £30 from the local tip .

[Techstar]

Re: LG 42PX5D - Clicking repeatedly

Did you ever get rid of the sparklies on this one tom , this seems to be a common problem on this model , i have had one where the pdp was the cause, a different lg model though.

[tom66]

Re: LG 42PX5D - Clicking repeatedly

Nope... Never got rid of them... sold it on cheap.
It's always the control board, never the PDP on LG's.

[Techstar]

Re: LG 42PX5D - Clicking repeatedly

Can the control board be repaired to cure the sparklies or is a replacement board needed. I had this problem on an hyundai plasma , coloured speckles which were coming and going sort of intermittent , i had a identical tv with good panels and i did a complete board change over i actually swapped over every single board , the sparklies were still there!

[tom66]

Re: LG 42PX5D - Clicking repeatedly

The panel ages meaning the timing needs to be adjusted.

So yeah, it's related to the panel, but the control board is what is needs repair -- a firmware update in most cases.

[Techstar]

Re: LG 42PX5D - Clicking repeatedly

Very good thank you.