60" LG Plasma 60PA5500 (Sound but no Image)

[precario]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

I checked voltage on my tv

VA:55
VS:205
VZB:120

Now here is where I run into a problem...when I connected my tv today I no longer have sound and on my main logic board I have a green blinking light...plus I have no back light...I attempted to check my VSC and VY and they just jump all over the place and I can not get a reading...can anyone lend me some insight on what may cause my VSC and VY to do that?

your tv may has a bad screen

[precario]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

if you replace the Y buffers and still the same problem the tv has bad screen

[Rl0089]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Sorry to revive an dead thread but I am trying to fix an LG 60PA5500 and I have the same issue. I removed the top left green board and did get the block bottom half picture back. I then replaced both of those vertical buffers(?) on the left hand side and the picture came back completely for about 5 minutes before going back to the same no picture issue. My question is, did I try the replacement board or is it the larger board directly to the right of those two vertical boards that needs to be replace? Sorry for my lack of terminology, I'm a beginner but i dable here and there. Thank you!

[Rl0089]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

One correction above, did I fry* the boards I installed or is it the other board that also needs to be replaced? Thank you

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

So I have the same issue with my LG 60” plasma 60PA5500; sound but no picture. I tried disconnecting the upper y buffer board and unfortunately when I took off the small ribbon it rested on the metal frame inside the back of the set and I plugged it in an pop! Direct short. I know I'm an idiot and still kicking myself for being so stupid.
So I replaced someone of the bad mosfets and after plugging everything back in I still get the tv to turn on and immediately shut off. I'm thinking the ysus board is fried but thought I'd ask for another option.
Would any other boards be shorted like the logic board or the y buffers?
Thanks for any feedback!

[Biruslapio]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

So I have the same issue with my LG 60” plasma 60PA5500; sound but no picture. I tried disconnecting the upper y buffer board and unfortunately when I took off the small ribbon it rested on the metal frame inside the back of the set and I plugged it in an pop! Direct short. I know I'm an idiot and still kicking myself for being so stupid.
So I replaced someone of the bad mosfets and after plugging everything back in I still get the tv to turn on and immediately shut off. I'm thinking the ysus board is fried but thought I'd ask for another option.
Would any other boards be shorted like the logic board or the y buffers?
Thanks for any feedback!

Hi, I have the same TV and my Y-SUS has a fried SMD resistor, could you provide me a picture or tell me what value it is?

https://www.badcaps.net/forum/showthread.php?t=94627

If I get mine working I can guide you better to what's happening with your set.

Did you unplug/plug buffer connectors with the TV on?

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

I attached a close up picture but cannot see any numbers on it.
If I unplug the power cable and logic board ribbon cable the tv turns on and has sound only, so which leads me to believe it's shorted.

[Biruslapio]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Thank you! It's a 2R2 then.

You probably damaged the upper Y-buffer, and what were the transistors that you replaced? There's a lot of fake IGBTs, this board uses 30F126, RJP63K2, these should be hard to find an original replacement.

Try removing upper Y buffer and testing the lower for shorts, this TV has a lot of problems with buffers shorting, and damaging the Y-SUS in the process.

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

I replaced the 30f126, 3 of them that were shorted. All others were ok. Once I replaced them and reconnected the board the tv turned on and immediately off. I checked these mofets after and they were shorted. I did checked them before turning on and they were good.

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Would you think I damaged the logic board also? I just don't want to dump tons of $ into this tv seeing I could replace it for less cash

[Biruslapio]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

I think the buffers and Y-SUS are the primary problem, the logic board should blink when the TV is on, remove both buffer boards from the TV and test Y-SUS + logic board + Z-SUS plugged in.

Powering on the Y-SUS with defective buffers will damage it.

I've uploaded pictures of both sides of the board with poorly circled points of interest.

First I've circled all the transistors that are on the heatsinks, they should not read short between any of the pins, most likely to fail are the 30F126 and RJP63K2.

All MOSFETs and IGBTs have gate resistors, if the transistor shorts, often these resistors have a current surge and go open-circuit, they're usually 10, 15 or 27 OHMs in parallel.

Those P105 SMD optocouplers that have 5 pins, they drive the transistors gate pulses and can short between pins too.

There's these 2W 2R2 PTH resistors on the component side, they act as fuses, when IGBTs go bad, they open too.

These are the most common failures on LG PA series Y-SUS.

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

I disconnected the buffer boards and it will turn on and immediately off. However i disconnected the power wires to the ysus board and the tv will come on and stay on with sound. Looks like the led on the logic board blinks as it's on. So I assume a new ysus board and buffer boards are needed.
What are the chances of the screen being fried?

[Biruslapio]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Small, but test the buffer boards when they arrive before you install them on the TV, I had to return 3 pairs of defective buffers that were sent to me as "working" before finding a good one finally.

Take a look at the Z-SUS since you said that the panel connectors shorted to the frame ground metal.

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Ok, thanks.
How do I check the zsus panel for being shorted; I checked the mosfets and they are not shorted to ground.
Could you also let me know how to check the buffers?

[Biruslapio]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Do not measure to ground, measure between the pins of the mosfets themselves, no shorts, it's fine.

Buffer test: Multimeter in diode mode, positive lead on buffer floating ground, negative lead on the output pins that connect to the panel, any shorts is a bad buffer chip. There's a handful of videos on youtube showing how to do that, search for "test plasma buffers".

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Ok thanks. I will do some testing.
If the zsus board is bad, wouldn't the tv power on and off right away like it does with the ysus board?

[Biruslapio]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

It shuts off because of current surge in VS, your Y-SUS must be shorted to ground somewhere, checking Z-SUS is just for safety, it probably survived.

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Just to be completely understood, when checking the buffers; you mentioned pins that go to the panel, is that referring to the screen connections or do you mean the pins to the ysus board?

[Biruslapio]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

This, where it's circled red use the positive lead, black = negative, will give you ~0.7V forward voltage, any less than that or if it's measuring less than MegaOHMs it's defective. Sometimes it's just one or two pins that short, so it's hard to pick up with a slow multimeter.

[living to camp]

Re: 60" LG Plasma 60PA5500 (Sound but no Image)

Surprisingly I checked both boards in the same way and did not find any shorts; unless I did something wrong.
I have attached a picture of the ribbon where it shorted to ground; looks to be the 4th one in on the upper y buffer when upside down. Not sure if that helps any.