LG 50PA5500-UA no pic

[Same]

Hello guys, I have a LG 50PA5500-UA-AUSLLHR Plasma that I acquired that has no picture. I have some skills and tools, but not fluid with all terms and procedures. My brother is better, who I will have assist me from time to time.

The tv was purchased new 2.5 years ago, the previous owner stated “This happened out of no where when I turned the tv on one night and the picture just didn't appear. It didn't happen while I was watching. No noises or anything occur and I can still change the volume and change channels no problem.” Addl: nothing has ever hit the screen and the screen ribbons on the left side look good under magnifying glass. I have taken the top y board out and the screen stays blank
Top y board has a short on the 1st connector In the group P101, bottom y board has no shorts. The set powers up, front led, main board led, control board leds all come on. Relays click, y board hums with faint ticking, all heat sinks heat up except the z board stays cold (laser temp reader), no caps are obviously blown however, there are a couple on the power board that could be, but doubtful.
I have hooked up an over the airwaves converter to coax and composite and I cannot get anything out of the set (sound or pic) the front led responds to the remote and I have also connected a USB drive which powers up, but again I cannot select the input for anything to show/sound. The green led on the control board blinks I think it stars out with long, short, pause repeat to long, long, short, pause repeat after it warms up. Some of this sounds familiar in many posts, but not in one single post so I get lost. When it is asked to check values for VS and Va I don’t know where to check it on the board and what should be nominal.
Any help would be great!
Thanks, Sam

[drussell]

Re: LG 50PA5500-UA no pic

Your picture is failry blurry but that sticker at top has the voltages printed on it, I just can't read them, and I can see the VS-TP (Vs Test Point) and VA-TP (Va Test Point) clearly marked on those jumpers in the upper right hand part of the power supply board so you could start by testing those with the red multimeter probe to the test point and the black to a good ground on the chassis.

I can't see enough to find the other test points, though, would need better pictures. Look for more things labeled like VE-TP on the Xsus board and a VSC-TP on the Ysus.

[Same]

Re: LG 50PA5500-UA no pic

Thanks for the reply, I couldn't figure out to get mutliple pics loaded. Va-55V Vs-205V. I found the jumpers on the psu board, but not the other on the y board or no exactly sure which one is the x board. Do I need to plug the y buffers back in to check for voltage on the psu?
Thanks

[drussell]

Re: LG 50PA5500-UA no pic

Thanks for the reply, I couldn't figure out to get mutliple pics loaded.

The FAQ for attaching pictures:
https://www.badcaps.net/forum/showthread.php?t=1868

Va-55V Vs-205V. I found the jumpers on the psu board, but not the other on the y board or no exactly sure which one is the x board. Do I need to plug the y buffers back in to check for voltage on the psu?

I'll be more careful here to use the LG parlance for the various boards. The different manufacturers use different terms which only adds to the confusion for those new to this stuff.

Don't plug the bad Y-Drive board (these are the long ones running up and down the left hand side, often called the "buffers") back in if it has a short, obviously you will need to repair/replace that before the TV is going to work. You will need to thoroughly check the Y-Sus board (Y-Sustain, the brown one on the left side which creates the sustain waveforms to drive the panel the that connects to the two upper and lower Y-Drive boards that connect the drive waveform coming from the Y-Sus to each row of the panel in succession from top down) for shorted transistors, etc. before you connect it up to a good upper Y-Drive board or if there is a fault it may well blow your good Y-Drive. A bad Y-Drive can often blow parts on the Y-Sus and bad Y-Sus can blow a Y-Drive. (Typically the topmost row is what dies, as you are seeing.)

The Z-Sus is the brown board to the right of the power supply (which I had called the Xsus but LG calls it Z; go figure) that is conected to the long brown board running up and down the right hand side which LG calls the Z-SUB board (which is often called a buffer, although it really isn't a buffer, just a connector board.) It is this Z-Sus board that will likely have the Ve or Vbias or whatever voltage test point since this is the side where the bias voltage goes to the panel.

In LG terminology the X boards are the address boards along the bottom of the panel which address each column on the panel. There are usually three, Left "X", Center "X" and Right "X" looking at the back. (Makes sense, X axis/Y axis but other manufacturers use other terms for the same functions.)

The small green board in the middle is called the "Control" board and the one to the right with the input connectors is called the "Main" board in LG-speak.

IIRC, the second line on the LG stickers below where it calls out the Va (the address voltage for the X boards at the bottom) and Vs (the sustain voltage that does most of the power, comes out the Y-Sus board through the Y-Drives) goes in this order: Set Up / -Vy / Vsc / Ve / Vzb

Some of these may be missing on some sets and say N.A. The Ve or Vzb (panel bias) test point is probably on the Z-Sus board but it varies, you'll have to look around.

Once you verify that your Y-Sus is good (at least no shorts, etc.) or repair or replace it, and upper Y-Drive is repaired or replaced, you'll probably be good to go.

Hope this helps!

[Same]

Re: LG 50PA5500-UA no pic

Thanks Drussel, I have better pics, I just wasn't sure on how to apply them at once, if anyone needs them I think I can do it now.

If I were to replace the y board and upper buffer I should be O.K. Assuming the panel itself isn't damaged.

If I understand correctly removing the upper buffer board test. If a lower half of the panel lights, then blown panel, which then means scrap the set.

Sam

[drussell]

Re: LG 50PA5500-UA no pic

If I were to replace the y board and upper buffer I should be O.K. Assuming the panel itself isn't damaged.

If I understand correctly removing the upper buffer board test. If a lower half of the panel lights, then blown panel, which then means scrap the set.

The panel is probably fine. The test with the upper Y-Drive disconnected is to see if the Y-Sus is working correctly. You may get a lower-half picture if everything except the upper Y-Drive is working OK. On some sets this won't work, though and I don't know for sure about yours. If the lower half lights up it doesn't mean there is something wrong with the panel but if you get a picture on the lower half you know your Y-Sus is working properly and just need a working upper Y-Drive.

You need to thoroughly check out your Y-Sus board for shorted FET/IGBTs at least (check in diode test or continuity mode between each combination of two pins of the three on each device in both directions) because, beware, if you try to run it with a shorted Y-Sus plugged into a good lower Y-Drive you'll probably blow the first row of the lower Y-Drive board and then need both upper and lower Y-Drive boards.

[Same]

Re: LG 50PA5500-UA no pic

O.K. that's encouraging because there are a lot of posts with this set and the dreadded "worn-through upper panel ribbon" causing the most upper ic to short on the upper buffer and perhaps damage the y-board too.

I'll work with my Bro on the diode testing and other to make sure the y-board is good.
Those upper y buffers are hard to find for a reasonable $$$

Thanks again

[Same]

Re: LG 50PA5500-UA no pic

Well its all a moot point. I lifted the top of the panel from the frame to check on the upper ribbon and what may be causing the pressure point on these sets and to confirm if this set is one of them. I found it Damn it! The upper ribbon has been compromised and has been rubbed through in a couple of lines. I have added a pic of the offending plastic tab (highlighted with whiteout) that is causing the damage and yes, if anyone has one of these sets they should try to remove the plastic and or part of the metal frame. I can see the same thing on the very bottom of the frame too! This is nothing other than a design flaw and there should be a recall. I'm going to try to make the repair if possible. If the upper y buffer has been shorted, would the y board automatically be bad too? What would be the sign/test/values to confirm a bad y board in this particular scenario.
Thanks,
Sam

[freakaftr8]

Re: LG 50PA5500-UA no pic

Wow! Thus is really starting to become a problem with this series. 50PA5500 and 50PA6500. There should be a sticky for this series to keep others from this dreaded imminent failure! Like a preventive measure. bunk design flaw!! Sorry. I'm pretty skilled when it comes to these TVs but unfortunately I wasn't able to repair mine. This is very very hard to fix if possible but I doubt it. And the problem is is you only have one shot with the new buffer board to see if it works because it will blow the IC almost immediately if the IC cannot make contact with all pins inside the panel.

[freakaftr8]

Re: LG 50PA5500-UA no pic

like others have said remove the upper board and try powering the set up with the lower board connected only you will get a lower half of the picture but it will be grey it will not have video feed if you get a grey or dark picture your Yboard is fine

[tom66]

Re: LG 50PA5500-UA no pic

I've seen a few pop up on eBay sound no pic - always go for high prices but I figure others don't know about this serious fault.

[Same]

Re: LG 50PA5500-UA no pic

I contacted a local authorized LG repair shop. He took all my details and contacted LG. Appearently there is a service bulletin on this and the screen has a 2-yr warrantee. He said it would be $50.US to look at it and between 125-150.US for labor. The $50.00 would go towards the repair to swap out the screen incl. boards! -control and main boards I think he said.
I have the set registered in my name, I just don't know the exact date of purchase nore do I have the receipt. Also, the electronics store it was bought from is now closed.
Will I have a problem with the warrantee since I don't have the reciept?
One last thing, I told the guy I scratched off some of the material of the FFC cable (I was going to try soldering it, but the copper traces won't take solder) so the cable looks a little narrley, would LG want the damage screen returned from the repair shop?