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

[living to camp]

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

Thanks for all your help Biruslapio.
I found a ysus board and buffer boards as a package deal online for $160; not the worst price but not the best.
I'm a little hesitant about sticking $ into this TV but I enjoy fixing things.
I have another question, does high voltage travel through the logic board or just video signals.

[Biruslapio]

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

High voltage should never reach the logic board, these pins that touched the metal frame you need to probe them if they go to buffer ICs or they are just jumpers or come from Y-SUS board and routes to lower buffer.

Since you got the whole package for $160 It's best to wait and install all 3 boards when they arrive.

That 2R2 resistor fixed my Y-SUS, tried it on just now and it's flawless, thanks again.

[living to camp]

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

Awesome that you got the y board fixed.
I took out the bad mosfets on my y board and put it back in and hooked it up; I know I was not going to get a picture, but the tv came on and stayed on with sound. I noticed on the x board that the heat shields got warm like they always did so I am thinking the x board is ok; would you agree?
I ordered the 3 boards so hopefully they will make it work correctly.

[living to camp]

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

So I received the new boards and installed them, so I'm back where I left off before I shorted the ribbon cable.
I don't have a picture but I have sound. I did notice that on the y board that the two lower heat shields do not warm up, but the two upper heat shields do. They also are warm on the z board.
I also tried removing one buffer at a time to see if half the screen came on but no change.
Any ideas what I could check for next?

[Biruslapio]

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

Measure VA, VS, VSCN, -VY and ZBIAS, they should be as stated on the panel sticker and stable (flat DC voltage), ZBIAS is on Z-SUS, VA and VS are on the power supply, VSCN and -VY are generated by Y-SUS, each board has a test point for the voltages.

https://www.badcaps.net/forum/showthread.php?t=59606

In this thread post #15 has information about the labeled voltages, except the TV there is a 50 inch PA6500, the boards differ.

[living to camp]

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

So I checked the points; readings are below:

VA....55 vdc
VS.....205 vdc
ZBias....2 vdc ( suppose to be 120vdc)
-VY....-10 vdc ( suppose to be -190 vdc)
VSCN..... could not find test point

I have attached a picture of the-VY testpoint I used and wanted to ask if it is the correct place to test.

So looks like too low of voltage; I'm assuming a bad y board?

[Biruslapio]

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

Are you testing between the + and - pins? Do not measure VSCN and -VY in relation to the ground, if these voltages are not up, control board is taking them down, what about during startup? If they are correct for a moment then it's something else.

[living to camp]

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

I put one of the probes on the -VY and the other lead on the ground of the tv. Is that right?

[Biruslapio]

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

no, that's exactly what is not to be done, there's a + and - on that picture you sent last, same for VSCN, two "grXXX" to put the leads on.

[living to camp]

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

Ok thanks for the direction to follow.
So, I checked the -VY and getting a reading of mostly 18 vdc; the voltage consistently changes anywhere from no voltage to 29vdc. At power up the most the voyage read was 30vdc.
The VSC terminals read from 1.5 vdc to no voltage. At startup it started up with a reading of 50vdc, then 120vdc then back down to 1.5 vdc.
I didn't see a VSCN terminal; would you know where it is?
So knowing the voltage results, is it leaning to the logic board or is there something more I could check or do? Thanks

[Biruslapio]

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

VSC = VSCAN = VSCN, it's just that some brands use VSCN, sometimes VSCAN on different models.

At this point I would probe all the IGBTs, MOSFETs and diodes, P105 optocouplers and gate resistors for transistors on both Z-SUS and Y-SUS.

[living to camp]

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

Can I check the vsc and and VY with the buffers disconnected or would that give a false reading?

[living to camp]

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

I was doing some checking last night and found that if I disconnected the upper buffer, the bottom of the screen lit up; if I had the upper buffer connected and lower buffer out, I got nothing.

[dick_barton]

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

Can you test the upper buffer board.
https://www.youtube.com/watch?v=3Oq2MsU0XOQ

[living to camp]

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

I checked the voltage at the VY and VSC with the buffers off and I get 186vdc at the VY and 147 at the VCS; it fluctuates; mainly stays at 147 but times it will rise up to 200 then go back to 147.
I am still only getting 1.85 at the ZBIAS no matter what.

Any ideas if there is something more I can check?

[Biruslapio]

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

dick_barton just requested to test the upper buffer, it must be defective, same case as my TV then, if this buffer is the one you bought, try return just it, the Y-sus and lower buffer are OK, retest the original upper buffer, you said in post #40 that it was fine, follow the advice in the video dick_barton posted to be sure.

[living to camp]

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

I'm sorry Dick_barton, I missed seeing your reply; I'll check them again and see if the buffer is bad.

[living to camp]

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

Well, don't know what to say..... I know I checked the buffers when they arrived and swear there were no shorts, but now I checked the upper buffer and sure enough, shorted.
So I checked my original buffer and checked twice and no shorts, so was a little hesitant to put it in since I shorted the ribbon cable, but I did anyway and the screen lit up! But I have a fuzzy picture and a horizontal black bar across the middle of the screen.
Still not getting the correct voltage at the ZBias, so where does that voltage come from?
Thanks, guys! I really appreciate all the patience and support!

[dick_barton]

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

You need to reseat the connection to the panel at the position of the black bar.
Don't forget with the set off.
Sometimes it does take one or two attempts to seat the ribbon correctly. This should get rid of the black bar unless....the buffer chip that drives that area is faulty.

[living to camp]

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

Thanks for the reply dick_barton.
So I reseated the orange ribbon and didn't have any luck; I guess it would not surprise me if the buffer chip is faulty; if you read earlier in my posts you will read a stupid move on my part.
I attached a picture of what I get now.
Still not sure why I'm not getting the correct voltage at the ZBIAS; only getting 2 volts
Thanks.