LG 50PA4500 - Sound with no picture

[tom66]

Re: LG 50PA4500 - Sound with no picture

Hold off on swapping them over for now.

Unfortunately (as above) these TVs have a -serious- design flaw where the ribbon cable (orange thing) that connects to the plasma "glass" can become torn, due to a mis-placed plastic notch.

This would, unfortunately, mean the TV is scrap! (Sorry) And your symptoms, of a top chip shorted, are very similar. So I am a little concerned.

Do you think you can carefully lift off the plastic facia of the TV (the front plastic) and have a look at the ribbon cable? The damage should be very obvious. From what I remember, the plastic is held on only by a single screw at the top. You can leave speakers etc. attached, and the stand on the TV, as it will make working on it easier. Just need to lift it down a little to check that ribbon. Be careful as the front filter glass may come off - it's the anti-reflective screen for the display.

[mincind]

Re: LG 50PA4500 - Sound with no picture

Tom66,

I had read earlier posts where this ribbon fretting was an issue.

In considering swapping boards, I chose against it....as my fear was I could potentially damage the working set when attempting to remove the board and ultimately have neither set work.

So....I am going to take my chances with a purchasing a "previously used" (which I think most nearly all parts are when the set is a few years old) upper Y-buffer board. I found one that will cost me $33.00 in total with 2-day shipping. So worst case, I will have spent $62.00 on a new Y-sustain and a Y-buffer board in an attempt to be able to use both TVs again. Figure it is worth the risk as opposed to outlaying another $1,200 for two new 50" TVs.

I will be sure to let you know if the replacement Y-buffer board is a success.

Thank you so much again!

Dante Mincin

[tom66]

Re: LG 50PA4500 - Sound with no picture

If you install the board into a set with a problem like this, the board will be destroyed very quickly, so I do not advise you try until you are sure it does not have this issue.

[mincind]

Re: LG 50PA4500 - Sound with no picture

Thank you for letting me know the consequence of installing a good board into a set with a torn/fretted orange ribbon cable.

But the way I understand it.....if the orange cable is bad - the TV is worthless - correct?

And I have no need for upper Y-buffer board I just purchased if the set needs to be scrapped.

So....perhaps I just blew $33 on a board - but I am going to take the risk...as I already ordered the board and I fear if I try to remove the plastic frame on the set, I may tear the orange cable in the process.

Rolling the dice.....

[mincind]

Re: LG 50PA4500 - Sound with no picture

Came home from Christmas Eve dinner at the in-laws and found a package at the front door...it was the upper Y-buffer I had ordered via 2nd day delivery.

Installed the board....and hurray - picture again!!

Thank you so very, very much for your help!! You can add another LG brand to your list of TVs saved from the scrap pile!

Merry Christmas!

Dante

[tom66]

Re: LG 50PA4500 - Sound with no picture

Cool. Would advise filing down the deadly notches - to avoid any future issues...

[mincind]

Re: LG 50PA4500 - Sound with no picture

I sure will...thank you again!

[pfranzek]

Re: LG 50PA4500 - Sound with no picture

Hello,

This is my first post.

I too have an LG 50PA4500 manufactured in April of 2012. The unit produces sound with no picture. First some history:

2 months ago, the unit would only click but not turned on. I found this site and followed one of the threads. It lead me to the PS and C802. I Checked the PS and found C802 was bulging. Replaced with same capacitance but higher voltage rated component. Unit turned on and worked. Thanks for the info.

Last week the unit was turned on, but only sound came out, no video. I followed this thread for a while, but have not been able to narrow down the cause. Here is what has been done so far:

1. Visual inspection of the boards. No damage found. Capacitors and components look fine.

2. Checked VS - measured 205.5 VDC. Sticker indicates 205 VDC.

3. Checked VA - measured 55.0 VDC Sticker is 55 VDC.

4. Checked VSC - measured 215.8 VDC. Spec is unknown.

5. Checked VY - measured 281.1 VDC. Spec is unknown.

6. Pulled upper buffer board off and checked for shorts. None found.

7. With upper buffer board off, powered the unit on. Screen was still dark.

8. Unit turned on in darkened room. No glimmer.

Can anyone suggest the next steps for TS of this unit?

Thank for the great info.

[pfranzek]

Re: LG 50PA4500 - Sound with no picture

Update:

Followed this post to find the voltages for VY and VSC:

https://www.badcaps.net/forum/showth...light=LG+Video

Sticker photo is attached. According to sticker, VY = 190 VDC. This unit is reading much higher!?

No value listed for VSC.

[Hamie]

Re: LG 50PA4500 - Sound with no picture

Just to make sure, you are testing -VY accross the test points or accross the resistor, and not to chassis ground?

[omendata]

Re: LG 50PA4500 - Sound with no picture

I suppose the good thing about having two identical tv's is that it should be a breeze to repair the broken one by swapping the boards from good to bad until you find all that are damaged although on the bad side of things you could blow the good boards you swap in if say the y-sus board gets damaged by plugging it in and the y-buffers are bad as well.

[pfranzek]

Re: LG 50PA4500 - Sound with no picture

Yes, I was measuring the voltage across the resistors for -VY and VSC as noted on the Printed Circuit Board.

BTW, Thanks for the reply.

[pfranzek]

Re: LG 50PA4500 - Sound with no picture

Thanks again for the replies.

Latest update. I missed this on the first exam. Found R283 on YSUS board is burnt. Will check Lower buffer board for shorts.

[pfranzek]

Re: LG 50PA4500 - Sound with no picture

No shorts seen on lower buffer board.

[pfranzek]

Re: LG 50PA4500 - Sound with no picture

Does anyone have any suggestions?

[pfranzek]

Re: LG 50PA4500 - Sound with no picture

Anyone have any suggestions?

[DHomerick]

Re: LG 50PA4500 - Sound with no picture

Just joined the conversation yesterday (24 Oct. 2015) My LG 50PA4500 has same problem (Sound no picture) I just disconnected the top left Y-buffer board, still no picture. VSC 0-6.5 vdc; VY 28-50 vdc. Do I reconnect the top y-Buffer and disconnect the lower Y-buffer?

[Moydalgan]

Re: LG 50PA4500 - Sound with no picture

I have been following this thread, but when I removed the buffer cards VSC & Vy continue to remain unstable! Does this mean that YSUS board is at fault?

[axj3oqg]

Re: LG 50PA4500 - Sound with no picture

Is this the end of the thread? I have same problem with Moydalgan with LG TV. Tried to disconnect both upper and lower buffer cards and still no picture. Any idea how to continue with troubleshooting? Thank you.