Lg50pg3000 sound but no pic.

[ron77]

This plasma television has sound, but no picture. Not a glimmer on the screen. Have checked all voltages and waveforms on main, power, control, y-sus, z-sus and buffer boards. Everything seems ok but there is no picture. Logic says probably plasma panel faulty. It could be, but have I missed something. D105 heat sink on power supply cold. The rest hot. Heat sinks on y board cool. Heat sinks on buffer boards cold. Heat sinks on z board slightly warm. So one section power supply not drawing current. Y board and buffers not drawing current. Z sus could be drawing a little current. Any ideas.

[tom66]

Re: Lg50pg3000 sound but no pic.

Did you check -Vy and Vsc on Y-sustain?

[ron77]

Re: Lg50pg3000 sound but no pic.

Yes Tom, I have. Vsc 134.8v. Vy 194.4v. Have also looked up info you put on this site on this model. Negative to left of resistors positive to right. Both readings come out positive.

[tom66]

Re: Lg50pg3000 sound but no pic.

OK, do you have a scope available? Does the screen glow slightly in a dark room ?

[ron77]

Re: Lg50pg3000 sound but no pic.

I believe it doesn't glow. At the moment can't tell, television facing window and impossible to darken room. Did work on it last night though and did look for any trace of brightness, and found none. I think safe to say answer is no.

[ron77]

Re: Lg50pg3000 sound but no pic.

Have scope.

[tom66]

Re: Lg50pg3000 sound but no pic.

Post a picture of your Y-sustain and I will highlight where to test. Any lights on control boarD?

[ron77]

Re: Lg50pg3000 sound but no pic.

Tom,
Spotted something, the buffers not connected to y-sus board. Looked ok, but not connected to correct slot. Vy and vsc voltages now incorrect when boards connected correctly. Know where I am now, maybe just one buffer faulty. Maybe both buffers and y board. Thanks for help.
Ron.

[Stingos1]

Re: Lg50pg3000 sound but no pic.

Sorry for jumping on thread, just joined so a pat on the back to all that contribute.

Just picked up one of these cheap and surfing net thought it was worth a punt,if I can fix it myself.

Same problem or do I have to start a new post?

Sound ok.

No picture at all,

Disconnected both buffers no change.

No heat at all on buffer heat sinks or y-sus board.

On powerboard 6 heat sinks warm one stone cold.

Only have a Beckmann hd110 to test for faults, can upload pictures no probs for help in identifying parts/probs.

Cheers Charlie

[ron77]

Re: Lg50pg3000 sound but no pic.

stingos1,
Didn't ignore you, only came back to report I had repaired my set. In my case, when both buffers connected correctly, voltages across r201 and r202 incorrect. Checked buffers, bottom buffer seemed OK on resistance readings and, as it turned out, was OK. Top buffer read 68 ohms across c116, c127, c137 and c147. Should read meg ohms. Out of circuit, about 7 meg. Top buffer faulty. Got brand new top buffer for £43 that is including VAT and postage. Part no. ebr50039008. Ebr50039005 equivalent. Some years back, with LG, if a buffer I/C went u/s, change buffer and y board. Could last some weeks without changing y board, but buffer would break down again. So with more modern board soldered every joint on print side. If I ran set with just bottom buffer, moving curtain effect bottom of screen, and heat sinks that were cold, get slightly warm. When fitted new buffer, worked straight away.

[Stingos1]

Re: Lg50pg3000 sound but no pic.

Replaced top buffer after finding continuity by checking both sides of ribbon connectors and adjusting vy vsc on ysus board think someone had tried fiddling with it previously when seller claimed they had it from new and no repairs to it.

Liars back panel screws had obvious damage and a couple stripped threads but I did not check upon collection

So I paid £40 for tv

New buffer £55 set now up and running

£95 and I have got 50" plasma in my front room

[ron77]

Re: Lg50pg3000 sound but no pic.

Seems your fault same as mine, in that changing top buffer got television working. Got my buffer from Charles Hyde. Having an account with them, apparently helps with price. It does seem that with LG the days of Y sustain boards knocking out buffer boards may have gone, with this model, anyway. What you have said does not surprise me, also had problems with back panel screws.
Anyway, well done Stingos,
Ron66

[tom66]

Re: Lg50pg3000 sound but no pic.

Have a friend with same TV, top buffer shorted. I also did a 42PG3000 with top buffer IC shorted (on single buffer board), that buffer was cheap though

[ron77]

Re: Lg50pg3000 sound but no pic.

Tom66,
Obviously a common fault with that model. Came across my first plasma with y board and buffer combined. It was a Samsung Ps50b450b1w. As long as buffer I/c's havn't gone it seems a kit will repair most of them. Also came across a Panasonic tx-p55vt30b, a kit repaired that y board. All three repaired now Tom, and am writing this to say how pleased I am to see the back of them. The last two, anyway.
Ron 77

[tom66]

Re: Lg50pg3000 sound but no pic.

A VT30? Call me jealous. Great panel! You should add a Kuro plasma to your repair list.

I find plasmas easier than LCDs to repair, just fixed a 50PS3000 I found by the side of the street, three FETs shorted on Z-sustain.