Lg 60PA5500 No picture

[WeadroW]

Hello everyone,
I have read numerous threads of similar model numbers but none seem to solve my issue. My Tv powers on and stays on like normal. All voltages are good from power supply to y board and z. The screen stays completely dark. I have purchased a new y sus board and installed. It did look like it primed and then no picture. It has not done this since the initial start up. I followed Tom66 suggestion to power one with top then bottom buffers disconnected. I do get the screen to light up in both cases. In fact with the top buffer disconnected from the ysus board but connected to ribbons and bottom buffer, the entire screen lights up.
I tried jumpering for the test pattern on the logic board with everything connect besides the lvds cable. No response on the screen at all. I did get a new bottom buffer, no change, and I am currently waiting on an upper buffer in the mail. Anyone have suspicions based on the screen images of what could be the culprit? Or if I have a blown ysus board, what component is failed?

Most of the screen images do have a constant blue bar on the right side of the screen. I'll have to upload the photos individually, it is only allowing 1 at a time. Thanks for the help!

[WeadroW]

Re: Lg 60PA5500 No picture

Here is a photo of the entire screen when it generated light after disconnecting the top buffer from the y board. I can upload all boards too if needed

[WeadroW]

Re: Lg 60PA5500 No picture

And here is a photo of when top buffer is disconnected entirely. One other thing I did not mention is the screen seems to respond when the input and menu buttons are pressed. There is a "white" image that moves around on the screen, possibly a "no input" that typically would appear when nothing is connected.

[WeadroW]

Re: Lg 60PA5500 No picture

To clarify, my questions are-
- Does this appear to be a Y sustain issue or a panel issue?
- would my upper buffer board be causing the set to have no picture at all when everything is connected?
-Is it possible I blew my new Y sustain board when I installed it with the original buffers?
The T con board has a 1 second 4 blink, then 5 second pause, then repeat. Thoughts?
Thanks

[Nick's Tvs]

Re: Lg 60PA5500 No picture

This is more than likely an issue with your boards and not the actual panel.
What kind of voltages do you get for VS and VA?
What kind of voltages do you get between the Y-sustain and the buffers?

[WeadroW]

Re: Lg 60PA5500 No picture

Thanks Nicks TV,
My incoming voltages to y sus-
Panel reads VA- 55v VS-205v

Cable from power supply:
7-5v- 5.05v
6-va- 55.0v
5-GND
4-GND
3-ns
2-vs- 204.2
1-vs-204.3

Reading voltages going from ysus to buffers I found that they were jumping around. The board makes a nice hum for about 2 seconds then a quiet chirp, then repeats. The voltages seem to bounce around with this sound.
I measured the test points of VSC and that was unstable bouncing from 13.97v to .8v. This was measured from the + and - VSC on ysus board.
I was able to get stable readings on the very bottom buffer connection. From top to bottom of the connector:
4.19v
0
2.43v
0
3.65v
3.64v
0
0
4.18v
.4v
0
4.98v
This is with the replacement ysus board. I can install the original and see if I get similar readings. I thought when I tested the original I was getting more steady readings.

[WeadroW]

Re: Lg 60PA5500 No picture

Update:
I switched back to my original y sustain and replaced the upper buffer with the one I ordered on eBay, and same results. No picture. I did get better, steady voltage on the outputs to the buffers. Most voltages were 18v.

What should the VSC voltage be? I was getting 50v.

I tried putting back the original lower buffer and it made a zap noise and I got a small puff of smoke after about 20 seconds.

I'm getting lost on this one. I'm not sure what I should check next. Should I try to unplug 1 buffer at a time to see if I get any images or screen response?

[Nick's Tvs]

Re: Lg 60PA5500 No picture

Wedrow,

That wouldn't be a bad idea, but I can tell you right now that you should be getting about 86 volts going to the buffers from the Y-sustain on that top connector for pretty much every pin and about 52 volts for VSC.
Try disconnecting both of your buffers from the Y-sus and see if your voltages are still oscillating. If they are then the Y-sus you got is also bad. If they are not and you are getting constant voltages, then it is possible one of your buffers is bad. Without the buffers in the system you will probably get a much higher voltage reading than 86vdc but what I am really interested in is if the voltages keep fluctuating or not.
If you do disconnect one of the buffers, make sure to completely and fully take them out of circuit. Also make sure to allow ample time for voltages to go back down to 5 volts or below before plugging things back in.

[WeadroW]

Re: Lg 60PA5500 No picture

Thanks Nick,
I will try later when i get home. I have a feeling my ysus board I ordered came in damage due to one of the caps on the corner getting pretty bent down I think it messed up one of the leads. I will try testing both y boards by themselves and report my findings if the voltage is still fluctuating.
If I do get steady voltage, and I install the buffers one at a time, and the voltage starts becoming unsteady, is that buffer likely the culprit?

[WeadroW]

Re: Lg 60PA5500 No picture

Alright here is what I've found:

Ysus board 1-
most pins showed -174v
VSC basically no voltage
VY 195.8v

Ysus board 2-
All voltages were Steady but negative?
Pin outs showed -96.6v very consistent
VSC -80v
VY- 88.2v

Board 2 with Top buffer only connected. Screen looked similar to my original posting pictures, screen primed.
Pin outs- -97.2v
VSC- 150v
VY- 87.7v

Board 2 with bottom buffer only.
Pin outs- 97.3v
VSC measured on the (-) terminal was -84v and on the (+) side was -97v. So when my meter was on (+) and (-) I got 13v. Which is the difference between 97 and 84. I'm inexperienced if this is normal.
VY -87.7v. When meter was on (+) and (-) I got 185v.

I did not try and put it all together yet. Guess I just don't want to blow anything just yet. But from my readings. Things seem like they should work?

[WeadroW]

Re: Lg 60PA5500 No picture

I connected everything back together and turned the TV on, the voltage started to oscillate again... So with both buffers running independently they work fine, but together something is making the ysus voltage unstable.
Is this a buffer or ysus problem?
Is there any way to dig into the ysus and determine what is failing?
I did try and disconnect the ribbon between the buffers with no change.
Am I able to disconnect each ribbon connector between the buffers and panel to isolate a possible problem with an ic or panel connection.

I'm just trying to narrow the problem so I'm not just throwing parts at the TV.
Thanks

[ReeceyBurger123]

Re: Lg 60PA5500 No picture

Zsus fault, likely high voltage coper coils have broken though the solder joints.

[WeadroW]

Re: Lg 60PA5500 No picture

Thanks Reecey-
Would this fault prevent the voltage on the ysus board from ramping up?
If I disconnect the Zsus board, would I at least get some sort of picture, or this model all or nothing?

[ReeceyBurger123]

Re: Lg 60PA5500 No picture

Yes Zsus could cause that, removing Zsus will cause image like what you have atm which is why I think its faulty.

[WeadroW]

Re: Lg 60PA5500 No picture

I checked the solder joints on the coils and they appeared ok. I did go ahead and re-solder them just for insurance.
I also tried unplugging the Zsus from the power board again, no change.
I'm getting 119v on the vzb.
The ysus board continues to have an audible chirp.
Should I check the coils on the y board? I'm pretty sure when I looked at the board those solder joints were ok. There has to be some link with having both buffers connected and getting the unstable voltage vs. 1 buffer and I get some sort of image on the screen.
Any ideas what component on the ysus board is not allowing stable voltage? Would I get any variation unplugging 1 ribbon at a time from the buffers.
Thanks!

[Nick's Tvs]

Re: Lg 60PA5500 No picture

As a rule of thumb and it only takes a few minutes anyway, but just double check all your axial diodes and all your transistors, fets, none axial diodes and any other components screwed into your heat sinks for shorts or low ohm readings.

[WeadroW]

Re: Lg 60PA5500 No picture

Do these solder joints look suspect? I have them on a few areas. I'll probably redo them anyways, but just curious if this could be my ailment. It looks like the isn't enough solder in the joint.

[WeadroW]

Re: Lg 60PA5500 No picture

I've included a picture of my ysus board. I'm at the point I believe both of these boards have issues. When measuring voltages, they are unstable going to the buffers. I almost want to try and see if I can make 1 good board out of the 2 bad before ordering another board.
Would the larger/higher output capacitors be causing the board to not produce steady voltages? Can someone tell me what the large square device is that had the silicon around it, I'm drawing a complete blank. Just trying to get some clarification before I order 1 more ysus.

[Nick's Tvs]

Re: Lg 60PA5500 No picture

Those solder joints are just fine.
Did you get any picture when the lower buffer was plugged in?
The large capacitors very very very rarely go out, I wouldn't even consider them to be a possibility. The large square is a transformer, also very rarely go out.
Have you checked your through hole axial diodes? That chirping sound that you are talking about has been known to be caused by bad axial diodes.
Also going back to you testing the Y-sus boards, you said one had negative voltage. That's probably because you just switched around your leads, and that's absolutely fine.

I think we need to take a step back and start over because this is all getting way to confusing. Lets try to be as simple as possible.

Back to original set up with Y1.
Symptoms are tv turns on but no picture. Power supply output voltages are all good. Voltages from y to buffers fluctuate however.
Which lines exactly are fluctuating and in what range.
Check the output pins of your Z-sustain to the panel, are those also fluctuating?

You replaced the Y1 with Y2.
After replacing y 1 with y2 you said you were able to get some sort of colors/picture to appear correct? Or was this strictly when one of the buffers was taken out?
If you did this test with y 2, did you also do it with y1 to compare?
Y2 also gave you non fluctuating voltages or were they also fluctuating but just less?
Any difference in the voltage readings between y1 and y2 aside from the fluctuation?

With the top buffer disconnected, you said you still got that weird picture. I don't recall you making any mention of what happened with the bottom disconnected and the top placed back in place.

Lets get all these questions straightened out first and then we can proceed further. At this point I don't even know if we are looking in the right direction or if we should look at the Z-sus.
If you could also take a picture of the back of the Z-sus for me, the last pic you posted was an up close. If you could take a picture from the top and from the back side as well. I just want to make sure I am thinking of the correct board here. The picture you showed us had only 2 inductors on it when it should have had 3 so I am thinking you may have just taken a pic of a different location.

[WeadroW]

Re: Lg 60PA5500 No picture

Nick, I agree reading through the thread that all the info I posted is confusing. I will start over and post my findings.
I do know that both y boards had stable voltages with no buffers connected, but the voltages were different.
I did check the axial diodes and. I thought they were ok, but I'll double check them.
I do get screen response with top buffer ONLY connected, and with bottom buffer ONLY connected. The picture is like the images I posted, nothing clear. With both connected, no image and unstable voltages.
I need to figure out how to get more then 1 pic to upload. But, I'll do these tests and report back.