Lg 50ps3000

[finntricky]

bottom half of screen working, but jumping and flickering.
top half flashes a pic every now and then for a split second.
so looking at this, its defo top buffer thats gone, maybe bottom on way out,
but what about Y-MAIN ?
power supply volts are as should be,what is the best thing to test first ?

[tom66]

Re: Lg 50ps3000

Could be control board or Y-buffer IMHO.
I would guess Y-buffer as LG's tend to have a lot of Y-buffer failures.
Signal is chained down from top to bottom, so fault with top can cause bottom to glitch too.
Y-sustain probably OK.

[finntricky]

Re: Lg 50ps3000

VSC volts jump up and down, then drop to 0v
vy seems to do the same.
this is with everything connected,
what volts should i have at these points ?
got no sticker with volts for them on screen

[finntricky]

Re: Lg 50ps3000

pics

[tom66]

Re: Lg 50ps3000

Picture of panel sticker please.

-Vy about -200V
Vsc about 150V

[finntricky]

Re: Lg 50ps3000

there you go tom

[tom66]

Re: Lg 50ps3000

Read in this order

N.A. / -Vy / Vsc / N.A. / Vzbias

So -Vy = -180V, Vsc = 150V, Vzbias = 105V

[finntricky]

Re: Lg 50ps3000

well something very wrong here then
vcs 110 - 130 up and down
vy 140 - 160 up and down.
and now going like this

[tom66]

Re: Lg 50ps3000

Looks like a buffer board popped. Try pulling the top board out and leave the bottom disconnected, do you get half a picture?

[finntricky]

Re: Lg 50ps3000

removed top buffer from y sus,no pic, buttom buffer still connected to y sus but not to top buffer

[tom66]

Re: Lg 50ps3000

Ok, will have to do it the hard way.
Pull both boards out and test them like in this video:
https://www.youtube.com/watch?v=51SZ...Y&noredirect=1

[finntricky]

Re: Lg 50ps3000

ok, well if i've done this right,
red probe on connecter pins that are all joined, and run black along screen connectors, both sides, im getting reading of 1100 plus, if i reverse the leads, i have no readings at all.

[tom66]

Re: Lg 50ps3000

Do you have a meter that beeps when you touch the probes? That's the best type to use. There can just be one pin bad and it will cause a problem.

[finntricky]

Re: Lg 50ps3000

no beep meter, just shows 000 when touching, and 1 when not.
i did move very slowly across the pins so i could see readings.
i can get new boards, but don't want to fit them, if the y sus is gonna take them out,

[tom66]

Re: Lg 50ps3000

Consider investing in a meter offering continuity - it is useful for testing these boards and locating other faults...

Check Vsc with Y-buffer boards out, if it is ~150V then it should be ok... It is very rare for any LG plasma sustainer to kill the buffer board.

[finntricky]

Re: Lg 50ps3000

getting 135 - 140v up and down, so thinking it should be ok,
im gonna put this tv to one side for the time being, as it also needs main input board as one of the HDMI ports is missing.
thanks for your help TOM, your the fella

[tom66]

Re: Lg 50ps3000

Are you sure about one port being missing? There's only 3 on these sets from memory, but the board is designed to accept up to 4 ports (50PS8000 only)

[finntricky]

Re: Lg 50ps3000

yeah thats right tom, 3 HDMI, 2 on back panel and one on side, its the upper one on the back panel thats missing, i did'nt see it was missing when i picked it up , LOL

[finntricky]

Re: Lg 50ps3000

update on this tv,
got a meter with the beep, checked the buffers and no shorts, bad news is i bought another pair before i got the meter,
but i still installed the new ones and got the same results.
thought id try auto gen, and just got red and pink spoty bars flashing on bottom of screen, not much different from pic above.
i think control board now, as the buffers check out ok on both pairs.
oh, and the voltages are 100% with this new meter.
any thoughts ?

[tom66]

Re: Lg 50ps3000

Unlikely to be control board, as most plasma control boards do not treat the top and bottom halves differently.