lg 42pc3dv sound, no picture

[duane.mosley]

first i want to thank topcat for starting this forum, i am a newb here and appreciate everyone that makes it possible for a diy'er like me to fix things. i have built my own dmx and rgb lighting controllers so i should be able to fix this i hope, with your assistance of course.

i have sound but no picture, when i turn the lights out and turn on the tv it stays pitch black, no grey screen. for starters the power supply voltage is 10v where it says it should be 5v. i am getting a reading of 419v on the vs pins on the power supply. all of my fuses are good except one on the ysus board. no caps are melted and there is no visual sign of damage to any parts. i have read some posts about replacing the sustain boards, and power supply but i would like to narrow this down without replacing everything. any and all assistance is much appreciated


thanks

duane

[tom66]

Re: lg 42pc3dv sound, no picture

I can tell you that 419V for Vs is incorrect; this would cause multiple capacitors to explode into near-earth orbit. A more sensible Vs is around 200V now notice 5V is also 10V... which is also double.

Your multimeter battery is flat, replace it.

[duane.mosley]

Re: lg 42pc3dv sound, no picture

i thought the 419v sounded kinda high considering the fuse is 250v. my meter has a 9v so i will have to stop tomorrow and get another battery. i did notice that neither heat sink on the sustain boards were getting hot. the y board seemed like it was getting a temperature, but not hot by any means. the z board was just plain cold.


duane

[tom66]

Re: lg 42pc3dv sound, no picture

There will be a rating on the plasma panel for Vs. For this chassis it's around 185~190V.

[duane.mosley]

Re: lg 42pc3dv sound, no picture

ok, so i was checking the voltage on the vac side of my meter, i switched to dc and my voltage is correct. i was unaware of this being transformed to dc,(rookie mistake) i have 5v on the power supply plug going to the y and z sustain boards as well as 188 on the vs.. both fuses on the z sus are good, one of the fuses on the y sus seems to be bad. the heat sink on the z board is cold, the heat sink on the y board is warmer than the z but that's not saying much. it is no where near as warm as heat sinks that i am used to. the tv has been powered on for over 30 minutes with the noise of static and the green light stays on. i removed the z board last night and did a continuity test and it looks like my ipm is bad. is the continuity test between the pins the only test for the sustain boards? if the z board's ipm chip was bad, wouldn't the fuses be blown?


thanks
duane

[tom66]

Re: lg 42pc3dv sound, no picture

Needs to be set on highest DC range, not AC..

[budm]

Re: lg 42pc3dv sound, no picture

"meter is set on 750v ac" should that be set to DCV?

[duane.mosley]

Re: lg 42pc3dv sound, no picture

i have my meter set correctly now. i am getting proper voltage to the sustain boards

[tom66]

Re: lg 42pc3dv sound, no picture

OK, can I have a picture of each of the sustain boards?

Also, what is the model of the plasma panel itself? It will be written on the ratings sticker (Vs: xxx Va: xxx etc) like PDP42G2#####. I can look up chassis wiring and particular tests for LG plasma panels now.

[duane.mosley]

Re: lg 42pc3dv sound, no picture

model number of the panel. pdp42v80201 hope these pictures are helpful. they seem kind of dark, if so, i will work up some more light

[tom66]

Re: lg 42pc3dv sound, no picture

OK, so on both ends of those white fuses you should see Vs or Va voltage. Do you?

SM: http://www.tgohome.com/ServiceManual...&Search=Submit

Panel datasheet isn't readily available, hmm.

[duane.mosley]

Re: lg 42pc3dv sound, no picture

t4.0AH 250v

[duane.mosley]

Re: lg 42pc3dv sound, no picture

were those the numbers you were looking for tom?



duane

[tom66]

Re: lg 42pc3dv sound, no picture

No, I was looking for you to measure the voltage on both ends of each of the fuses on the boards.

[duane.mosley]

Re: lg 42pc3dv sound, no picture

[QUOTE=tom66;309333]No, I was looking for you to measure the voltage on both ends of each of the fuses on the boards.[/QU

my apologies, i appreciate your assistance. 60v and 189v. i do have one bad fuse on the y sustain board.

[tom66]

Re: lg 42pc3dv sound, no picture

A bad fuse on the Y-sustain would therefore cause no picture. From the faulty fuse, test both ends to the ground (chassis of TV) on 2000 ohms, what do you measure?

[duane.mosley]

Re: lg 42pc3dv sound, no picture

024 on the one leg that didn't have power, being the rookie i am, i didn't turn the tv off before putting the meter on the hot leg and now my meter won't measure ohms. i am running across the street to get the neighbors meter now

[tom66]

Re: lg 42pc3dv sound, no picture

Ah, oops; sometimes the meter's built in resettable PTC fuse will reset after cooling down for about an hour.

[duane.mosley]

Re: lg 42pc3dv sound, no picture

i have a dead short on one of the fuse legs. the leg opposite of power supply. so much for just a fuse! lol

[tom66]

Re: lg 42pc3dv sound, no picture

In which case you need to replace the IPM.

https://www.youtube.com/watch?v=Y8MNQYXw8E0

(Different fault, but the IPM has failed nonetheless. You only need to replace the Y-sustain IPM.)