LG50pg3000 no picture just sound

[shaunbt123]

Hi there
can someone please advise me of what to look for with regard to this lg plasma tv.there is sound when i plug my xbox into it using the hdmi port just no picture at all.
ill just let you know what simple tests ive tried so far (im not an electronics expert)
1.. i have replaced the ysus board

2.. i left the set switched on for 20 mins. then unplugged. then felt the heatsinks on the y and zsus boards(with the power off and unplugged) all were still cold.

3.. only two of the heatsinks on the power supply board were warm the others were cold.

4..looked at the screen in complete darkness there is no glow to the screen

5. the power light is on front of tv is green .

6. there is also a click from a relay on the powerboard,when pressing power button on from standby.

i hope its not the panel thats gone.
thanks for your time.
shaun.

[capkid]

Re: LG50pg3000 no picture just sound

Your panel is most likely ok.

- Have you checked the voltage output from the power supply to the Y-Sus and Z-Sus?
- Are there any blown fuses on the Y-Sus or Z-Sus?
- Was your replacement Y-Sus new or used?

Pics of your chassis would be helpful.

Edit: This thread may also be useful: https://www.badcaps.net/forum/showthread.php?t=18892

[shaunbt123]

Re: LG50pg3000 no picture just sound

thanks for your response
i have
checked the voltages vs=191v,,,va==64v on ysus board
all fuses checked ok
i have disconnected top buffer still no picture
diosconnected bottom buffer and get sort of a picture in the top half of screen,but has lines in it.

[tom66]

Re: LG50pg3000 no picture just sound

Bottom buffer possibly at fault then.

[shaunbt123]

Re: LG50pg3000 no picture just sound

thanks for the reply.
Im going to order both bottom and top buffer boards,as i have read its better to replace them together. will update on how it goes when there fitted.
thanks again.
shaun.

[shaunbt123]

Re: LG50pg3000 no picture just sound

ok heres the update.
its not good,i bought all 3 boards ysus board, top and bottom buffers,switched on and got a full screen of picture but had lines through it.i then swiched off and unplugged as i was going to reseat the ribbon cables,switched on again and no picture at all.
think im just about giving up on this.
thanks shaun.

[capkid]

Re: LG50pg3000 no picture just sound

- Did you do anything to the TV (ie. adjust ribbon cables or detach and reattach connectors) between the time that you turned it off then turned it back on and got no picture?

- Were the lines you saw horizontal or vertical?

- Do you still have sound?

- Did you try removing either of the buffers?

- Did you recheck your voltages, including Y-Sus generated voltages?

[shaunbt123]

Re: LG50pg3000 no picture just sound

hi there
all i did was to disconnect and reconnect the ribbon cables that go to the buffers,this was after power was switched off.

the lines were very thin horizontal black lines.
i still have sound.
i tried removing one buffer then the other,but get a blank screen.
the voltages on the ysus board are vs-191volts and va-65volts.
thanks again
shaun.

[capkid]

Re: LG50pg3000 no picture just sound

What are your Vscan and -Vy voltages on the Y-Sus? Any blown fuses?

[shaunbt123]

Re: LG50pg3000 no picture just sound

hi there.
sorry to sound dumb,but can you tell me where i measure the vscan and -vy voltage on the ysus board.i have tested fuses and are all ok.

[shaunbt123]

Re: LG50pg3000 no picture just sound

i have just found two resistors at the bottom of the board,underneath one it says vsc and under the other it says vy are these the test points i need to measure.

[tom66]

Re: LG50pg3000 no picture just sound

Yep, you will probably need to measure across them, red probe on end / black probe other end, Vsc = Vscan.

[shaunbt123]

Re: LG50pg3000 no picture just sound

hi again guys,
i checked the voltages they are as follows.with the buffers attached the voltage goes up to around 50v then drops off to the following.
vscan=0v

vy=0v

but if i unplug both buffer boards the voltages are as follows.
vscan=135v

vy=195v

im only guessing but does it look like its fried the two new bufferboards.

thanks for your patience.
shaun.

[shaunbt123]

Re: LG50pg3000 no picture just sound

is there a way of testing the buffers to see if they have shorted,or could it be a different problem.
thanks.
shaun.

[tom66]

Re: LG50pg3000 no picture just sound

It looks like your buffers are bad as your voltages drop when they are connected.
Buffers removed from cracked screen TVs often are bad.
http://www.youtube.com/watch?v=51SZsfH60EY

[shaunbt123]

Re: LG50pg3000 no picture just sound

thanks tom i tested the buffers as the video shows ,sure enough both are showing bad,the only thing i dont understand is why i got a full picture on screen when i first used them.
ps when i installed the replacement buffers i also installed a replacement ysus board at the same time but all three parts were used and not new.
thanks for all your info so far.
shaun.

[Jim1590]

Re: LG50pg3000 no picture just sound

just a thought, but a bad y sus could have burned out the y buffers. Did you get all 3 from the same seller? I assume you got them on ebay.

so possibly the buffers were good until they got hooked up then a bad y sus fried them.

just shooting in the dark here, but I have had this happen to me.

[shaunbt123]

Re: LG50pg3000 no picture just sound

thx jim for your reply.
yes i got all 3 boards together at the same time from a shop on ebay.is there a way to test the ysus board so i can tell if its going to fry the next buffers i get.
thanks.
shaun.

[Jim1590]

Re: LG50pg3000 no picture just sound

I myself have tested y sus before to my 90% satisfaction and finger crossing before plugging it in.

As for your board, I am not sure. I was just throwing a thought out there and will leave it to the guys who have done more plasmas to say yea or nay.

[capkid]

Re: LG50pg3000 no picture just sound

It sounds like your Y-Sus is fine.

Did you try re-installing your original top buffer and disconnecting one of the bad bottom buffers? It's a little risky, since you could fry your old top buffer, but it might give you a better idea as to the health of your replacement Y-Sus. I always have my hand on the power cord when I'm testing plasma picture issues, just in case I notice something "funky", so I can pull power right away and possibly avoid damage.