LG 50PA6500 - Sound no Picture

[Josh094]

Hey guys, I've got an LG 50PA6500 with sound and no picture. I have taken the back off it at this stage and the boards appear to be in good health. There is however a buzzing sound coming from the y-sustain board when the tv is switched on. I have taken a flashlight to the screen and can't see any images or cracks.

Any help appreciated, thanks in advance.

[capkid]

Re: LG 50PA6500 - Sound no Picture

It sounds like a bad Y-Sus. Have you checked PSU output voltages to the Y-Sus and Y-Sus generated voltages (VSC and -VY)? There should be two resistors near the buffer connectors on the Y-Sus for checking VSC and -VY (R272 and R273).

[Josh094]

Re: LG 50PA6500 - Sound no Picture

Thanks for the help, as the TV is out at my brothers place I'm unable to check these currently but when I get the chance I will do so and report back. If it is the Y-sus board will it simply be a matter of replacing it? Thanks again.

[capkid]

Re: LG 50PA6500 - Sound no Picture

Yes, you could just replace it if it's faulty. More than likely, the buffers connected to the Y-Sus are fine, but you'll want to at least closely examine them for burned buffer chips. I'd also check output voltages to the Z-Sus (mainly VS and VA) and the VZB voltage on the Z-Sus to make sure it's working correctly. There's a resistor at R412 to check the VZB voltage.

Edit: I'm not familiar with this TV, so it might help to post a pic of the circuit board layout.

[tom66]

Re: LG 50PA6500 - Sound no Picture

Make the room pitch black, can you see any glow emitted from the display panel? Some other users on this forum have glowing screen no picture caused by main board failure instead of Y-sus.

[Josh094]

Re: LG 50PA6500 - Sound no Picture

Hey guys, didn't want to bump an old thread but this saves me starting a new one. I went ahead and replaced the Y-sustain board and I now have picture and the TV seems to work, however the picture quality is bad. It seems really grainy (unsure of how to describe this) and images tend to linger after being left on screen for a few minutes before fading away (looks like burn in, they seem to go away after a few minutes though). Quite sure it's not related to the video source as it looks the same at the lg splash screen and on all inputs.

Is this likely to be caused by a board, or is the panel just bad? It had no picture when I purchased it (mentioned above) so I'm unsure of the condition of the panel when it was working. Just wandering if there is a simple fix for this or if I'm better off just cutting my losses and moving on, thanks guys.

Here are some pictures of the issue, sorry for the bad quality. (opted not to embed, some are quite large)

http://i270.photobucket.com/albums/j...ps76d5840a.jpg

http://i270.photobucket.com/albums/j...ps3170ec0a.jpg

http://i270.photobucket.com/albums/j...ps966860c1.jpg

http://i270.photobucket.com/albums/j...psf2268017.jpg

[capkid]

Re: LG 50PA6500 - Sound no Picture

I see what's called "mal-discharge" or commonly called "sparkles" in your pics. Have you verified that your voltages are set correctly? I know that the older LG plasma TVs can have mal-discharge issues when a sustain board is replaced.

[Josh094]

Re: LG 50PA6500 - Sound no Picture

I'll be doing this ASAP as I don't have a multimeter with me at the moment. Are there are any other points where I should check voltages? Thanks, will report back with voltages when I get the chance to measure them.

[kosman]

Re: LG 50PA6500 - Sound no Picture

Hi

I have the same problem Sound no in LG 50PA6500

Prelim verified

VZB R412 = 142V
VY R272 ~0V-20V Oscilloscope show hiccup like a protection activate
VSC R273 ~0V-2V Oscilloscope show hiccup like a protection activate

After I try to removed Y Drive Top (LG EBR73763902) and then re measuremnt

VZB R412 = 142V
VY R272 = 182V (No hiccup)
VSC R273 = 144V (No hiccup)

Could you help to advise from my experiment? Is the Y drive Top problem?

[arttd]

Re: LG 50PA6500 - Sound no Picture

Hi

I have the same problem Sound no in LG 50PA6500

Prelim verified

VZB R412 = 142V
VY R272 ~0V-20V Oscilloscope show hiccup like a protection activate
VSC R273 ~0V-2V Oscilloscope show hiccup like a protection activate

After I try to removed Y Drive Top (LG EBR73763902) and then re measuremnt

VZB R412 = 142V
VY R272 = 182V (No hiccup)
VSC R273 = 144V (No hiccup)

Could you help to advise from my experiment? Is the Y drive Top problem?

Hi Kosman. Just wondering if you ever solved this, or what your final outcome was. Thanks!

[freakaftr8]

Re: LG 50PA6500 - Sound no Picture

well I have gotten quite familiar with this model. On the Y sustain board if you measure a short across the vs c.a.n resistor nearest the buffer boards then your buffer Board is shorted. Your vs and VA voltages will pulse and not get a steady reading.

[tom66]

Re: LG 50PA6500 - Sound no Picture

Buzzing sound can also be chipped panel, on edge of glass or such.

[kosman]

Re: LG 50PA6500 - Sound no Picture

Sorry for lately reply, i don' t know for the meaning of the VS C.A.N. Could you help to give me full name?

My last solution, i had order Y Sus and Buffers Board from Ebay and chaged its but i still found the same problem when i connect the Buffer Boards to Y Sus.
The Y Sus will shutdown (hiccup voltage at Vy & Vsc)
So i had suspect the cause of failure came from pannel.
But i don't know how do i prove pannel is good or no good.
If anyone have suggestion please let me know.

Thank you

[tom66]

Re: LG 50PA6500 - Sound no Picture

freakaftr8 has a thread on the 50PA5500 which is similar, ribbon short against plasma panel frying buffer board. Not sure if it got fixed.

[freakaftr8]

Re: LG 50PA6500 - Sound no Picture

Yes this is an issue! Better yet I was wrong about my model number, it was a typo. It's actually the same model as yours. The boards I ordered are.for the 6500 but same tv.

Koman. Disconnect and remove completely the upper buffer board. Power up the tv. Do you have a lower half functional?

[arttd]

Re: LG 50PA6500 - Sound no Picture

Yes this is an issue! Better yet I was wrong about my model number, it was a typo. It's actually the same model as yours. The boards I ordered are.for the 6500 but same tv.

Koman. Disconnect and remove completely the upper buffer board. Power up the tv. Do you have a lower half functional?

That's EXACTLY what my 50PA6500 is doing. Please tell me you know what's going on. This thing is driving me crazy! I've been going round and round on this for 3 weeks now, and can't find anything wrong on any of the boards. I was about ready to just assume it was the panel, and write off my losses.

[tnrmanring]

Re: LG 50PA6500 - Sound no Picture

That's EXACTLY what my 50PA6500 is doing. Please tell me you know what's going on. This thing is driving me crazy! I've been going round and round on this for 3 weeks now, and can't find anything wrong on any of the boards. I was about ready to just assume it was the panel, and write off my losses.

Hate to bump again but I am new, can't post my own yet and I am having the same issue. No picture, just sound. just stopped one day. Never acted up before it just went out and then about 6 months ago I am watching TV and it just goes.

The screen stays black... i think. I haven't had it in a pitch black room to find out.

my problem is that I took it to a repair person and when he used his DMM to test the power (at the plugs on the boards)he said that all the boards are getting power to them and the panel is likely bad... which I didn't know could happen to a TV that I had only had for a year out of the box. Especially a TV that had never been dropped, banged, struck, slapped, power surged, or even called bad names. I was very protective of my TV... and I am at a loss. The only other thing I can remember is that the LED on the video board are glowing steady red. Not sure if that means much...

[tom66]

Re: LG 50PA6500 - Sound no Picture

Unplug top buffer. If set works on bottom half: 90% chance your panel is bad. Test the buffer IC to confirm. You will find a tear in the ribbon.
https://www.youtube.com/watch?v=51SZ...Y&noredirect=1

MAJOR design flaw by LG, plastic breaks off screw hole and eats into the ribbons...!

[tnrmanring]

Re: LG 50PA6500 - Sound no Picture

Unplug top buffer. If set works on bottom half: 90% chance your panel is bad. Test the buffer IC to confirm. You will find a tear in the ribbon.
https://www.youtube.com/watch?v=51SZ...Y&noredirect=1

MAJOR design flaw by LG, plastic breaks off screw hole and eats into the ribbons...!

im sorry.. im lost... where would the tear be? do I have to take off the panel to see it? the repair man called and said that he took the top buffer off and it gave him a half picture and said pretty much the same thing but he didn't say it was the ribbon. what is the IC? im not good with abbreviations. are you saying that if I test the board like in the video and its bad then it might be the board or am I screwed either way? sorry to be such a bother... but I want to learn! thank you for your help! I guess I could always sell off the parts if all else fails.

[tom66]

Re: LG 50PA6500 - Sound no Picture

The ribbons are the little orange things going into the glass of the panel.
The tear is often very hard to see. It's hidden on the other side sometimes. For me, I had to use a magnifying glass to see it. It will be on the top ribbon cable most likely.