LG 50PA5500-UA Black Screen, sound on

[S77]

Hi everybody,
have 50PA5500-UA plasma tv with black screen now.
Started from screen blinking, some times was black screen, some times was ok.
Then it stopped turning on. Standby light, press ON button, CLICK tried to turn on, another CLICK right away - turn itself off, standby on.

Unpluged Z-SUS with Y-SUS (power cable goes from PS board to Z-SUS then from Z to Y-SUS), tv turned on.
Z-SUS pluged in, Y unpluged - tv turned on.

So does it means Y-SUS or Y-buffers are bad?

Checked top Y-buffer connections, all clear.

Should i replace all 3 Y boards or i can check smth before?

Please help

[freakaftr8]

Re: LG 50PA5500-UA Black Screen, sound on

Remove the upper y buffer board off the equation and then power it up. Do you have a grey raster on the bottom half of the screen?

[S77]

Re: LG 50PA5500-UA Black Screen, sound on

No, just blank screen (after remove upper y-buffer)

Funny thing, that after i connect everything back and Y-SUS to power supply, no tv still starts ok, and sound works

[freakaftr8]

Re: LG 50PA5500-UA Black Screen, sound on

With ysus and zsus disconnected can you verify vs voltage from the power supply

[S77]

Re: LG 50PA5500-UA Black Screen, sound on

so i have black screen with or without Y buffer boards, tv starts but no picture

[freakaftr8]

Re: LG 50PA5500-UA Black Screen, sound on

That's correct. You will not have a screen at all with the Y buffers disconnected. However you need to verify if you're still receiving vs voltage from the power supply with or without the buffers connected to the ysus board. Without monitoring output voltages from the power supply you have no way of telling if your power supply is going into protection mode with the buffers installed therefore you can't physically tell if your buffers ar shorted unless you doing ohm test

[S77]

Re: LG 50PA5500-UA Black Screen, sound on

So i have to check voltages on ps board or ysus board? This ysus board getting voltages from zsus board. It doesnt have any power cable from ps board to ysus directly
Please advise what exactly should i check with meter?

[sordids999]

Re: LG 50PA5500-UA Black Screen, sound on

set you meter on dc 600 volts (red lead on test point black to chassis of the tv )then use the VS/VA test points on your power supply to see if they match up with your panel which should have a sticker attached giving voltages VS/VA/VSC/VE etc
try this with YSUS/ZSUS unplugged first

[S77]

Re: LG 50PA5500-UA Black Screen, sound on

Just tested vs and va without ysus and zsus boards. Read correct numbers as on board table: vs 203, va 54

[S77]

Re: LG 50PA5500-UA Black Screen, sound on

Guys, what should i check now? Meter vs, va with zsus or ysus connected?