LG 50PA6500 Plasma TV damaged after a power spike

[tofik]

Hello, I have an LG 50PA6500 Plasma TV, purchased new in 2012.
Unfortunately plasma is not working at all after a power spike.

Qucikly tested the PSU and voltages seems to be okay, when eveything is disconntected from the PSU I got:
VS = 200-206 / actual = 205 V,
VA = 55 / actual = 54.9 V,
M5V = 5.2 / actual = 5.19 V,

17 = 17.24 V,
5.2 = 5.19 V,
STDBY = 5.19 V,
ERROR_DET = 4.8 V - does it mean PSU is damaged? the rest of the voltages seems to be fine.
what's your opinion about the PSU?

Also I just ordered a new logic board (EAX64290701) as IC102 was getting extremely hot when the power was on.

I am afraid that the main board also could be damaged (EAX64696604). The status LED on the main board (Q500) is always off, no matter if the logic board is connected or not, didn't check Y-SUS and X-SUS boards yet.

I don't really have an experience in the field but I see these modules are quite cheap to order so I believe it's fixable. At least I can try.
What are the chances that PDP panel is damaged after a power spike?

BTW. I found this tweak for a better black https://www.youtube.com/watch?v=GlFDzMaQ3Bs, have anyone tried it?

Thanks everybody for reading.

[Biruslapio]

Re: LG 50PA6500 Plasma TV damaged after a power spike

power spikes either come through the psu or mainboard, and stop there, have never seen it spread to other boards, in this case it probably came through HDMI or antenna cable.
your psu seems to be working, error det is probably emitted by mainboard, if you unplug it from the psu, does the panel lights up with a black screen?

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

Thanks for your message!

error det is probably emitted by mainboard, if you unplug it from the psu, does the panel lights up with a black screen?

Error det is 4.8 V when psu is disconnected from the main board and the others modules as well. Is that fine then?

Tomorrow I will try to disconnect the main board and check if the panel lights up with a black screen as you mentioned.

[tvtimmy]

Re: LG 50PA6500 Plasma TV damaged after a power spike

Run the test patterns to see if the mainboard is bad.

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

Run the test patterns to see if the mainboard is bad.

How to run it?

Standby led is always off if it's important to mention.

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

To test the main board, I completely disconnected it, connected back the logic board and the PSU, same like in this instruction https://www.youtube.com/watch?v=gPP3yw06MVw

Unfortunately the LED on the logic board is not blinking at all, is completely off so I think logic pcb is dead, today I'll receive the new one for further tests.

But I am still not convinced that the PSU is fine as Error_det is 4.8 V (which is high?) even when the PSU is disconnected from the main board and the others modules.

this is my PSU, VS, VA, M5V, 17V, 5.2V, STDBY - these all seems to be okay but I need to mention that I can't hear any relay clicking when I power on the PSU.

[Biruslapio]

Re: LG 50PA6500 Plasma TV damaged after a power spike

For the self test all you need is the VA, VS and M5V, led not blinking is very suspect so test again when the new board arrives.
It is done by shorting those two pins circled on the image.

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

Update,

I received a new LOGIC PCB, now I see that the status LED on it is blinking (so the logic board definitely was damaged) but it's blinking only when the main board and YSUS board (EAX64282201) is disconnected.

Today afternoon I will have a new main board but the problem is also YSUS board.








You can see that two tracks were burned, I restored them but it still doesn't work.
I quickly tested few components and diode D562 (as marked on red) is very likely damaged, resistance on both end is 0,4 ohm.

Probably it will be difficult to fix this YSUS pcb and replacement is not that cheap like a logic and mainboard

The problem also is I am not sure it will work even when YSUS is replaced.

Any suggestions?

[nomoresonys]

Re: LG 50PA6500 Plasma TV damaged after a power spike

trace repair: https://www.youtube.com/watch?v=mFMkfAyqBMc

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

trace repair: https://www.youtube.com/watch?v=mFMkfAyqBMc

I already fixed both traces before, that's pretty easy but ysus is still dead.
I mean any suggestions what could I do now? Ysus seems to be a hard thing to fix I guess. New one is expansive.
I probably would go with that and get one if that would be the last thing I need to do, PSU, logic, motherboard, zsus - these all seems to be fine.
I am afraid that after replacing ysus I will find out that PDP panel is damaged and all my effort is pointless.

[nomoresonys]

Re: LG 50PA6500 Plasma TV damaged after a power spike

test the easy things on y-sus, diodes, resistors, last one I took my y-sus board out and tested the transistors for shorts, it's just easier to get at from the bottom of board and you can also see if there's anything obvious, like something burnt etc, if you do take board out for testing, MAKE SURE when you put it back in that you tighten EVERY SCREW do not skip any, can easily short something out by not making sure, in my case y-sus was ok, my z-sus had all shorted igbt transistors, switched them out just to discover both y-buffer boards were shorted out, lol, just another plasma tv nightmare, some testing there: https://www.youtube.com/watch?v=aZF57Bok7Ws

[nomoresonys]

Re: LG 50PA6500 Plasma TV damaged after a power spike

a little more testing there, you can probably find your exact model with some searching, there's a lot of videos on plasmas on youtube: https://www.youtube.com/watch?v=8Dfgfh6mK0I

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

Thanks for the links! I will check it later, I mean the components on the YSUS pcb.

Is it possible to check if the PDP panel is working fine without a YSUS board? I think ZSUS is in good condition, same like PSU, mainboard and logic.

Aslo I just realized that not the track is burned out but the resistor R267, does anyone know what's the value it could be?

[R_J]

Re: LG 50PA6500 Plasma TV damaged after a power spike

It is just the trace that is burnt, R267 is not burnt, it is in series with R269. It looks like the source for the voltage is D255, so I would check all the components connected to D562 anode

[Biruslapio]

Re: LG 50PA6500 Plasma TV damaged after a power spike

this board is not beginner friendly to repair, a lot of things go wrong with it at once, you'll be checking on the Y + Z boards, all transistors and diodes, all the smd resistors linked to IGBTs, and their switching optocouplers(TLP105).

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

Hi again,

I did some further tests with the Y-SUS board, it doesn't really look good.

I tested all transistors for shorts to gnd and also between drain/gate/source. Resistors, diodes and capacitors also has been tested for shorts.

- all traces has been restored, beside these two traces mentioned before, visibly nothing else looks bad on the pcb,
- diode D562 is definitely damaged, I desoldered it from the pcb and resistance is 0 ohm,
- diode D256 is 3 ohm (test on the pcb so far), probably also damaged,
- transistor Q509 - all legs shorted, took it off from the pcb, tested again, confirmed > all legs shorted,
- also found a short on Q401 + Q402 + D401 - desoldered them all, tested and Q401 + Q402 are definitely damaged (short between legs number 2 to 3), D401 seems to be fine.

The rest of the transistors seems to be fine, no shorts to gnd and no between their legs.

Did not test smd resistors linked to IGBTs yet.
About switching optocouplers (TLP105) - what's the easiest way for testing them?

Any suggestions what to check now? I don't have any obvious shorts on this PCB now but feel there will be something else damaged, what do you think?

Is there any chance to test the PDP panel without these mosfets on the Y-SUS? May I give it a try?


some photos:

[nomoresonys]

Re: LG 50PA6500 Plasma TV damaged after a power spike

check both buffer boards for shorts too, some videos of it on youtube.

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

I will.

Q401 and Q402 are both RJP63K2, Q509 is: K8A60DA.
Any chance to test PDP without them?

[nomoresonys]

Re: LG 50PA6500 Plasma TV damaged after a power spike

I'm not sure on that question, have not worked with a lot of plasmas, dislike them intensely, lol.

[tofik]

Re: LG 50PA6500 Plasma TV damaged after a power spike

I will try, it should not make any damage I think. Probably won't work but lets try before I install the new ones.