LG 50PA4500 - Sound no Picture

[vtyler84]

I got my hands on a free plasma TV and am trying to figure out why I have no picture but sound (fuzzy sound, nothing's plugged in).

Only test I've done so far after reading on this forum is I unplugged the top buffer board. When I did that the bottom half of the screen lit up grey for a second before dimming. I plugged it back in did the same test with the bottom board and the screen stayed all black.

Does this mean my buffer board needs to be replaced. I was going to test it until I realized my multi meter doesn't have a continuity setting, unless someone can tell me how to do it without that setting?

Another common problem I read with these tv's is with the power board and a bad capacitor. I bought some capacitors before I found out that there was sound so I've kind of ruled out the capacitor being an issue now with sound...

Thanks!

Tyler

[maxvalutech]

Re: LG 50PA4500 - Sound no Picture

Tyler if you want some assistance please read the stickies on latest page and then test all the important voltages on the power board connector/s with set in standby and at switch on and put those in a post complete with good pics of the whole board setup and individually. Test sound etc with a proper signal connected.

[vtyler84]

Re: LG 50PA4500 - Sound no Picture

Update.
Finally got the TV home and can work on it now in the evenings.
Attached are the pictures of the back of the TV.

Doesn't look like there are any bad caps etc.

Did some power tests.
Va: 55V
Vs: 205V
Vy, Vsc were jumping all over the place. I was using dc and testing across the resistor? Any other tests that need to be done?



Thanks. Any help would be appreciated.

[tom66]

Re: LG 50PA4500 - Sound no Picture

Test -Vy and Vsc with the top board disocnnected.

With the panel on and top disconnected, press MENU or other keys and see if the bottom half works.

[vtyler84]

Re: LG 50PA4500 - Sound no Picture

Disconnected top buffer board from the y-sustain board, my reading wasn't stable jumping all over the place.

Tried to get a picture on the lower half by pushing the settings button but nothing changed. Bottom half still a faint gray colour, with a solid black line about 1 inch from the bottom and 1 pixel thick or so. I'll try with a dvd player and try to change the inputs but need to find a spare HDMI cable first.

I am assuming I need to leave the buffer board attached to the screen? ie orange cables?

[vtyler84]

Re: LG 50PA4500 - Sound no Picture

Tried my DVD player with HDMI. Because I can't see what I am doing not sure if I got it to go to the HDMI input. In either case nothing changed on the screen. Just a dimly light bottom half of the screen when the upper buffer board was unplugged.

[tom66]

Re: LG 50PA4500 - Sound no Picture

OK, try unplugging both buffer boards; are the readings on -Vy and Vsc stable now?

[vtyler84]

Re: LG 50PA4500 - Sound no Picture

Unplugged both buffer boards from the sustain board and the readings are still all over the place.

To be clear I'm measuring in DC Volts? Across the resistor correct?
See attached picture.
White Arrows for VY
Red Arrows for VSC.

[tom66]

Re: LG 50PA4500 - Sound no Picture

Yes, this is correct.

In which case, you probably have a defective Y-sustain.

It is probably worth testing the Y-buffer board first. https://www.youtube.com/watch?v=51SZsfH60EY

[deegee2016]

Re: LG 50PA4500 - Sound no Picture

I have an LG47ODUE that shows LG Logo then goes black under torchlight image is visible.


Power supply board tests:

Standby voltages: in order on connector:

9) Ground - Ground = 0.0v
8) 12v - NC = 11.95v
7) 12v - 12v = 11.95v
6) Ground - Ground = 0.0v
5) 24v - 24v = 24.77v
4) Ground - Ground = 0.0v
3) 3.5v - PDIM2 = 3.54v
2) 3.5v - PDIM1 = 3.55v
1) PwrOn - DrvOn = 3.42v

Most voltages not present until standby button is pressed

Led Connector Tests:

106v down to 82.2v at led connector on both lines. LEDs connected

115v down to 82.2v at led connector on both lines. LEDs disconnected.

Diode Side Test: (red probe to cathode side and black to test points at led connector)

97v and decreases - cathode side of diode to test point at led connector.

LEDs have been checked out of the unit on a DC power supply two strips at 30v all LEDs work.

Work has been carried out previously as jumpers on led strips. Work fine out of unit on DCPS.

I had image but no backlight.

Could this be a caps issue???

Does the TV need all LEDs connected to work correctly (ie) cut out if not enough LEDs for load.

Obviously 88.2v is not enough to drive the leds
Kind regards Dee

[dick_barton]

Re: LG 50PA4500 - Sound no Picture

I have an LG47ODUE that shows LG Logo then goes black under torchlight image is visible.

Hello Dee,
Your better off starting a new thread or it becomes quite confusing dealing with two sets in one thread.

Edit.
Is that the correct model number?

[budm]

Re: LG 50PA4500 - Sound no Picture

https://www.badcaps.net/forum/showthread.php?t=64716
https://www.badcaps.net/forum/showthread.php?t=64714
Posting at multiple thread is not going help, especially if your model number does not match the OP of the tread.

[deegee2016]

Re: LG 50PA4500 - Sound no Picture

Sorry ppl, I was having trouble posting. Noted

[tom66]

Re: LG 50PA4500 - Sound no Picture

Sorry ppl, I was having trouble posting. Noted

If you read the PM that is sent to every new user it tells you that you need to post a reply in the "introduce yourself" thread before you can post. Basically you need 1 post before you can create threads. Stops the majority of spambots.

[Niemannc]

Re: LG 50PA4500 - Sound no Picture

Hi guys. Can anyone help me with this same tv

[Andrew F. Ali]

Re: LG 50PA4500 - Sound no Picture

Hi guys. Can anyone help me with this same tv

Maybe we could if we knew what is the issue with your TV. You would get better responses if you started a new thread for your TV and issue.