Panasonic TX-P42S30 green/red sparkles

[Hombre]

Hi

Bought this set, it had 7 blinks, SN board shorted. Replaced 4 30F131 (altough just 3 were dead) and that removed short from SN2. Powered it on and it came on for a second or two, dark/gray picture with some black horizontal stripes appeared. That changed SOS to 6 (discharging). Investigated a bit more and found Q441 (DG302) that measures around 400 ohms between 2 legs. I assumed that isn't quite normal, and it seems that was correct, because i replaced it and tv works now. It does turn on, no SOS, almost everything is fine .
I noticed that picture isn't quite as it should be, it has red/green sparkles, best noticeable on gray background. On black background i can't see none. And it looks like there is some ghosting, or bad discharge, because when i enter menu, then turn it off (menu, not tv) i can still see some menu.
When tv is on, led on both SS and SN are green.
Vsus is 215V, and Vda is 58V. There are trimpots on PS for Vsus and Vda, but didn't mess with them, waiting for some ideas first
I really don't know if someone was changing some boards before i bought it, but it doesn't look like it is.

[Hombre]

Re: Panasonic TX-P42S30 green/red sparkles

I don't want to open new thread so i'll post here.
I have another 42S30, SN board shorted. Changed 4 igbt's (q401, q402, q421, q422 - all 30f131), and it gone short again.
With sn2 and sn20 disconnected - 8 blink sos.
Checked SS board for shorts, and it is ok as far as i can tell. I think that i read somwhere that disconnected sn2 and sn20 can also give 8 blink sos, any chance that someone can confirm it.
I changed again those 4 mosfets altough one of them was ok (q402) plus ic502 and q531, based on repair kits sold on ebay.
So before i plug it in i want to be sure that ss isn't the one that is killing my sn board. But as long as there isn't short on ss Vsus line i think it could not affect on SN board? Am i right?

thx!

[tw2005]

Re: Panasonic TX-P42S30 green/red sparkles

As far as I know, SN20 or SC20 disconnected will trip SOS8. The SS is not connected to the SN so i would not expect it to kill the SN. maybe something else was blown on the SN that killed them again or maybe the buffer ICs are shorted?

[tom66]

Re: Panasonic TX-P42S30 green/red sparkles

What you are seeing is called plasma dithering and is completely normal. It is due to how the panel is driven. Plasma panels can struggle with low-intensity variations so to compensate they rapidly dither between levels which when viewing from a distance of more than a few feet is hidden and blends into the picture properly.

[Hombre]

Re: Panasonic TX-P42S30 green/red sparkles

Ok, thx guys!

Well, pluged it in, green blinking light and when panel is about to turn on, pop, shorted q401, q402 and q422. Interestingly, q421 survived - again.

[tw2005]

Re: Panasonic TX-P42S30 green/red sparkles

Tough one.

On the SN , should be a tag TPVFG & TPSN1 maybe see if low or shorted. Also TPVFG to the output pins of the buffers.

Probably not the issue but can't hurt to have a look.

Also these are the group of parts in cct where it blew those transitors.

R522,IC521,R525,R506,C505,Q521,R517,R421,R422,Q421,Q422,D421

R501,IC501,C502,R503,C503,Q501,R512,R401,R402,Q401,Q402,D401

I see the SJ kit has 4 transistors,4 resistors, 2 diodes and screws, so we could assume the 4 transistors you've replaced, gate resistors, D401,D421 , RF1501NS3S ?

For more clues, 15pce kit, Q401,Q402,Q421,Q422,Q621,Q531,D401,D421,IC502,Q6??,R???,R???,R???,R???,R???

GTVWatford
PARTS Q401 Q402 Q421 Q422 Q441 D401 D421
PLUS IC502 AND Q531 WILL FAIL IN 20% OF CASES

[Hombre]

Re: Panasonic TX-P42S30 green/red sparkles

Tested TPVFG to the buffers - no short there. TPVFG to gnd, and TPSN1 to gnd no shorts either.
All resistors in that area are ok and within specs. I'll double check those ic's.

SJ kit probably consists of 4 30f131, gate resistors, 4 7.5ohms, and those rf1501ns3 diodes.
On this 15 pcs kit those resitors are probably gate resistors (7.5ohms), plus one probably for q621.

3 times blown q401, q402, q422. Diodes are ok, gate resistors are ok. Last time replaced ic502, q531 altough they measured ok, but that didn't help either.

I could never find those easy fix pany's, it's always something little extra .

[tom66]

Re: Panasonic TX-P42S30 green/red sparkles

PZ80s are easy fix. I've done 10 so far - with bad cap on MC201/MC301 module.

[Hombre]

Re: Panasonic TX-P42S30 green/red sparkles

I know, but i had p42y85 on which a board was bad (5v line shorted iirc)

[Hombre]

Re: Panasonic TX-P42S30 green/red sparkles

Any ideas what can cause this q401 q402 q421 q422 go short to ground? I am trying to debug it, but everything seems ok, altough something obviously isn't.

Also these are the group of parts in cct where it blew those transitors.

R522,IC521,R525,R506,C505,Q521,R517,R421,R422,Q421,Q422,D421

R501,IC501,C502,R503,C503,Q501,R512,R401,R402,Q401,Q402,D401

Tested all of this, once i remove those shorted igbt everything listed looks ok. Anything else can make mess?
It's always the same pattern - q401, q402, q422 (or q421 - i am not sure which but one always survive that failure) go short - other stuff looks ok - no obvious shorts.
If panel is shorted, is it possible that none of the buffer ic's fail, how to test shorted panel, don't know what else to look

[tw2005]

Re: Panasonic TX-P42S30 green/red sparkles

Don't have any great ideas, maybe check resistance across pins 3,5 ic521, 5v line

pins 5-6,5-7,5-8 on pc461. potshots really.

[Hombre]

Re: Panasonic TX-P42S30 green/red sparkles

OK, to close this one too

Replaced blown Q401 Q402 Q421 Q422 (all 30F131). Since i tested all resistors, diodes next logic step to me was to change those drivers for these blown IGBTs. So changed IC501 Q501 and IC521 Q521.
Installed SN board, connected buffers and SN20, plugged it in, 7 blinks. Waited for a few minutes so caps can discharge and then plugged SN2. Fingers crossed, pluged it in and it came on

Everything works great, and btw i installed those safety washers (don't know how it is said in english ) on all bolts, because there were some arcing marks on few places due to loose bolts.