LG Plasma 50PC1DR- Y-SUS Issues

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

LOL !!! it took me 2 minutes to remove an ipm with this thing. guys, if you do a lot of rework.. buy one !!! best 200$ even spent on a tool. an hakko 808...

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

I did a test here, took IPM J016 ER from board #2, put on tv#1.

now doesnt shut down, i see a black screen with green dots, then all white image for 2-3 minutes then shut down. image is white but with a lot of weird lines in it.. colored lines.

bare with me here, just trying to figure out things. first time on a such thing...

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

okay.. found that VSC is completely off, it's oscillating between 0-10v. -YV is 223vdc..
im using the good test points. something's completely off here !!!

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

That looks like you might have a short circuit.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

on the y-sustain ?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

ive swapped the buffer boards, the z-sus, the j016 ipm so far.

is vsc and -yv generated on the ysus ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Yes. Is the problem present with the buffers connected?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Yes. I've tried removing the buffers and it didn't change anything.

The exact behavior of the tv right now is, startup with black screen with green dots, then after a few secs goes to a funky white screen and i can hear sound (noise from tuner), then flashes back to black screen with green dots, and shut down.

-yv measure 223vdc, vsc measured from 0-10 vdc fluctuates.

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Vsc controls the setup waveform of the panel so if it is missing you can get odd symptoms such as wild brightness fluctuations. Can you see what's connected to the Vsc and trace it out, see if there are any more shorted FETs etc...

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

I'm going to dig a bit more in the service manual and that training manual to see if i can understand something...

I've tried 3 different ipm's on the same tv same Ysus board, and had 3 very different results...

But, similar is the vsc. it never changes from ipm to ipm, it's always completely off.

Is the vsc generated by the IPM ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

No, VSC is generated by that little sub board with the transformer on it.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

i restored -YV 196v, found 2 big 100 resistors again under one ipm. i missed those..

I guess i'm giving up until i get some new ER ipm's to test the board.

I will check, might be a short on the sub board !

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

VSC is bad still?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Um - can i power one one of these plasmas without any of the 2 ipm's to check if the VSC is present ?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

VSC is bad still, yes !

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

You should be OK on powering it up without IPMs but beware high voltage will not decay quickly on some plasmas without a load.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

I got 120vdc at the output of the subboard. So it's doing it's job.. it's after that that vsc is being lost !

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Is there a way to figure out (when the service manual doesn't say anything about it) the wattage value of a SMD resistor (the ones i'm looking for are marked 100, as 10 ohms..) ?

Doing a search on digikey, even with the same dimensions, i get results from 1 to 16W, huge difference !

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Measure the dimensions and use these approximations.

0.06" x 0.03" = 0603 = 50-63mW
0.08" x 0.05" = 0805 = 80-125mW
0.12" x 0.06" = 1206 = 125-330mW
0.20" x 0.12" = 2012 = 500-1000mW

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Okay. They are a little bigger, they seem to be 2512;

0.248" L x 0.126" W (6.30mm x 3.20mm)

I just have a ruler though. Is 1W sufficient for this size ?

I'm still trying to find out what's shorting the 120VDC vsc after the sub board. from what i understand, this is being sent directly to the y-drive output?

I see Q2, Q3 there, also Q13, 05 (can't find this Q05?).. all seem fine

I'm trying to figure out what's a 4A67 diode and a 25 diode. Google results are a *bit* confusing to me !

I'd really like to find out what's draining the vsc down from the sub-board that generates VSC. i see VS coming in, VSC going out, then if i check output at the VSC test points it's 0-10 volts. I don't understand !!!