LG 50pg20 no picture/sound fine (pictures included)

[RAYMOND88]

Yesterday the plasma tv picture turned black while watching. i have power and sound is good. I am trying to determine whether i need to replace ysus, top or bottom y buffer and how to test them. I tried disconnecting all connections from to main panel but still black. Next I tried disconnecting the top y buffer and half the screen turn a lighter shade of black but still no picture. i disconnected the lower y buffer and no results just black screen. I do not see any bulging or blown/leaking caps. I have a digital multimeter just need some direction on where to test to narrow down or single out the part i need to replace. I did put a temp probe on the following heat sinks. xsus warm, main warm, y top buffer warm, y bottom buffer warm, ysus cold. thanks for the advise this is my first tv repair but i learn quick.

[RON_CET]

Re: LG 50pg20 no picture/sound fine (pictures included)

ok first thing look on your y-sustain which is board to left which also connects to upper and lower ydrv board.. see if any of the fuse or open and also like wise on your z-sus? next if no fuse or blow then lets measure our VS&VA voltages coming from power supply,there a label on the panel that will tell you want those voltages are suppose to be most common fault for no picture would be y-sus failure

[RAYMOND88]

Re: LG 50pg20 no picture/sound fine (pictures included)

ok first thing look on your y-sustain which is board to left which also connects to upper and lower ydrv board.. see if any of the fuse or open and also like wise on your z-sus? next if no fuse or blow then lets measure our VS&VA voltages coming from power supply,there a label on the panel that will tell you want those voltages are suppose to be most common fault for no picture would be y-sus failure

I checked the ohms and the fuses read good at about 2.0. I see the label but how do i check the vs&va? where do i place the red and black probes?

[RON_CET]

Re: LG 50pg20 no picture/sound fine (pictures included)

red probe would go to pin or connector mark VA then black would be chassis ground,looking on your y-sustain board you'll see the connector and it will have the pinout connections label there for VA & VS measure each seperate with respect to chassis ground while powering set on

[RAYMOND88]

Re: LG 50pg20 no picture/sound fine (pictures included)

red probe would go to pin or connector mark VA then black would be chassis ground,looking on your y-sustain board you'll see the connector and it will have the pinout connections label there for VA & VS measure each seperate with respect to chassis ground while powering set on

With my multimeter on V-AC, red probe on va and black on ground and set on i do not get a consistent number it jumps way up and down. what is the proper setting for the multimeter and procedure to test step by step. Also how can I check the y buffers. thanks

[tom66]

Re: LG 50pg20 no picture/sound fine (pictures included)

You need to use VDC. Use the metal frame, e.g. screw holes, as ground.

[RON_CET]

Re: LG 50pg20 no picture/sound fine (pictures included)

set your meter to dc volts reading for around 200 volts scale or higher also to check your voltages for VS & VA, this link may help give you and guide of how to check your buffers
http://blog.coppelltvrepair.com/2010...er-boards.html

[RAYMOND88]

Re: LG 50pg20 no picture/sound fine (pictures included)

You need to use VDC. Use the metal frame, e.g. screw holes, as ground.

Ok i checked the V,va and vs and they are correct as per the label. They read 5V/va- 60V/vs-194V Does this eliminate the ysus as a bad component?

[tom66]

Re: LG 50pg20 no picture/sound fine (pictures included)

No, but it does eliminate the PSU. The buffers and sustain could still be faulty.

[RAYMOND88]

Re: LG 50pg20 no picture/sound fine (pictures included)

set your meter to dc volts reading for around 200 volts scale or higher also to check your voltages for VS & VA, this link may help give you and guide of how to check your buffers
http://blog.coppelltvrepair.com/2010...er-boards.html

As far as my buffers go when i disconnect them i am left with the male ends on the buffer and the female end with the pins are left on the ysus. top buffer read 1.07 ohm whether i reverse probes or not and bottom buffer is more sporadic and does not stay on one number but its around 3700k ohm or 4-38m ohm depending if i reverse the probes. the coppeltv illustration reverses the probes and im not sure if im doing it right??

[RAYMOND88]

Re: LG 50pg20 no picture/sound fine (pictures included)

No, but it does eliminate the PSU. The buffers and sustain could still be faulty.

In your opinion what and how do i check next?

[tom66]

Re: LG 50pg20 no picture/sound fine (pictures included)

You get 1 ohm on your top buffer? That's a dead short. Bottom buffer is probably okay.