LG 42pt350 A little help.

[elchochito]

Ok, I'm a newbie in this forum and I'd really appreciate any help I can get.

My LG will not turn on. It will stay on standby click a couple of times, and then goes back to stand by. I replaced the power supply and the y sustain board, that however, did not fix the problem.

Is there any way to test the mainboard? If someone could push me in the right direction, it would be greatly appreciated.

thank you.

[newtothis]

Re: LG 42pt350 A little help.

Can you give me a close up pic of the control board

[elchochito]

Re: LG 42pt350 A little help.

Can you give me a close up pic of the control board

Thanks for your help.. i'm attaching a pic of the control board and the main board.. let me know if these are ok.

[newtothis]

Re: LG 42pt350 A little help.

Yes brilliant.

Unplug the TV.

Take a piece of wire and connect the two holes marked as red in the highlighted area on the pic

Unplug the LDVS cable (the one that goes from control board to the main board)

Turn the TV on.

You should see test patterns, do you?

[newtothis]

Re: LG 42pt350 A little help.

LOL I forgot to hit the upload button

[elchochito]

Re: LG 42pt350 A little help.

LOL I forgot to hit the upload button

did the process with the wire, and still the same thing.. tries to turn on twice and goes back to standby.. thank you for your quick reply btw

[newtothis]

Re: LG 42pt350 A little help.

Main is probably fine then.

[elchochito]

Re: LG 42pt350 A little help.

Main is probably fine then.

i figured. where can i go from here? anything else i may be able to test to find out where the problem is?

[tom66]

Re: LG 42pt350 A little help.

Before you declare main to be OK please check PSU Vs/Va to see if they come up or not. Is the plasma panel a PDP42T1#### (this is written at top of back metal.)

[elchochito]

Re: LG 42pt350 A little help.

Before you declare main to be OK please check PSU Vs/Va to see if they come up or not. Is the plasma panel a PDP42T1#### (this is written at top of back metal.)

Mr Tom.

My plasma panel model # is PDP42T3####

VS voltage will make my meter fluctuate, but won't get more than 1 volt on it.
VA Same thing, when i turn the plasma on, the meter jumps up and goes down w/thin a fraction of a second.

[tom66]

Re: LG 42pt350 A little help.

OK now unplug Y-sustain and Z-sustain (big left and right hand boards.) Do Vs/Va rise higher?

[elchochito]

Re: LG 42pt350 A little help.

OK now unplug Y-sustain and Z-sustain (big left and right hand boards.) Do Vs/Va rise higher?

removing both tv actully turns on, i can hear the volume loud, but no video. voltages are
va 55.4v
vs 202 v

thanks tom, i think we're getting somewhere now.. i just replaced y sustain board. But, apparently that wasn't the problem.

where can i go from here?

[tom66]

Re: LG 42pt350 A little help.

OK, see this manual (search 42T1, close to 42T3) to see where to test Vsc and -Vy. Plug Y-sustain in, but leave Z-sustain disconnected.



They should compare to the rated voltages on the sticker.

[elchochito]

Re: LG 42pt350 A little help.

OK, see this manual (search 42T1, close to 42T3) to see where to test Vsc and -Vy. Plug Y-sustain in, but leave Z-sustain disconnected.



They should compare to the rated voltages on the sticker.

Thanks Tom, I really appreciate it. I found the locations I need to test through the service manual you provided. I have one question. The y-sustain feeds from the z-sustain. Is there anyway to bypass that? Or some other way to test. I attached a pic to the back of my tv.

[tom66]

Re: LG 42pt350 A little help.

Hmm, OK, I forgot about that design on this TV. Can you see what the TV does with the Z-sustain plugged in but the Y-sustain disconnected from the Z-sustain?

[elchochito]

Re: LG 42pt350 A little help.

Hmm, OK, I forgot about that design on this TV. Can you see what the TV does with the Z-sustain plugged in but the Y-sustain disconnected from the Z-sustain?

When i unplug the y-sustain board the plasma goes back to its original symptoms. attempts to power on twice and then goes back to standby.

[tom66]

Re: LG 42pt350 A little help.

It sounds like your Z-sustain is bad then.

To test:

Unplug Y- and Z-sustain power cables on Z-sustain. Power from TV disconnected for a couple of minutes before proceeding.

Check between VS and GND on 200 ohm range. Reading should start low then climb to overload (O.L or single "1".)

Repeat test for Y-sustain.

[elchochito]

Re: LG 42pt350 A little help.

It sounds like your Z-sustain is bad then.

To test:

Unplug Y- and Z-sustain power cables on Z-sustain. Power from TV disconnected for a couple of minutes before proceeding.

Check between VS and GND on 200 ohm range. Reading should start low then climb to overload (O.L or single "1".)

Repeat test for Y-sustain.

When i do this, i'm only getting .4omhs. With just the zsustain. I'm ordering a replacing zsustain board and report back. thanks for everything tom, let me know if theres anything i may have missed.h

[newtothis]

Re: LG 42pt350 A little help.

Yes that is shorted

[tom66]

Re: LG 42pt350 A little help.

Repeat the test on the Y-sustain, and test your old one too.