LG 42PJ350-UB won't power on all the way?

[pilotguy251]

I am troubleshooting my LG 42PJ350-UB, and it will not power on. I purchased a new Power supply for it about a month ago, and then a new main board earlier this week. Upon putting in the new parts, I get something I wasn't before, but it still won't power on fully. The relays click, the screen lights up for about a second, then the relays click again, along with a green LED on the logic board, and the set goes back off. And as long as the TV is plugged in, the cycle continues. About five or so seconds between off and partway on. What's going on here and is there any way that I might be able to fix it? I'm thinking about just giving up and parting it out if I can't get it working again.

[Andrew F. Ali]

Re: LG 42PJ350-UB won't power on all the way?

Could it be the backlights then??

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

Well, they do light up, and before I got the new mainboard, I could power up the set and the backlight would stay on until I unplugged it.

[CapLeaker]

Re: LG 42PJ350-UB won't power on all the way?

So if you force the PSU on with the main board disconnected, the backlights come on and all the voltage rails come up?

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

That's what it did at first, now it just clicks right back off after a few seconds with the new board in, even if it's disconnected.

[CapLeaker]

Re: LG 42PJ350-UB won't power on all the way?

Well... I guess you either swap or fix that PSU first.

[Alastair E]

Re: LG 42PJ350-UB won't power on all the way?

42PJ350 is a PLASMA TV set,

http://www.lg.com/uk/tvs/lg-42PJ350-plasma-tv --Therefore, has NO Backlights.....

Sounds to me that the Control-Board is Detecting fault on either Y-SUS or Z-SUS and shutting down the set....

Start by checking all the voltages while the set is running--for the short time it does...

Voltages such as Vs, Va, VSC, -Vy, and VZ-Bias are important and if way out can cause the Control-Board to detect fault and shut down.

[CapLeaker]

Re: LG 42PJ350-UB won't power on all the way?

pictures folks... pictures!

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

Yeah, upon testing the voltages for the short time that it comes up, they go up to about 180 on the leads before it goes down.

[newtothis]

Re: LG 42PJ350-UB won't power on all the way?

Please provide pictures of your boards and overall layout of them all connected please

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

Hope this helps

[newtothis]

Re: LG 42PJ350-UB won't power on all the way?

Ok can you test the VS, VA etc as stated in post #7 and list them for us

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

VS peaking at 186v for the short time that it comes up and the VC is at around 60v. Nothing on the grounds, NC 180v and M5 V 5v

[newtothis]

Re: LG 42PJ350-UB won't power on all the way?

VSC, -Vy and VZ-Bias?

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

Are those on the power supply board? Don't see any of them labeled that just yet.

[newtothis]

Re: LG 42PJ350-UB won't power on all the way?

Couple highlighted here

Have to hunt around for -Vy

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

110v through the VZ, 293v through the VSC, and still hunting for the -Vy

[Alastair E]

Re: LG 42PJ350-UB won't power on all the way?

Picture of the Panel Label too please--Has the vital Voltage Info on it....

[newtothis]

Re: LG 42PJ350-UB won't power on all the way?

Voltages

Va : 60v
Vs : 205v
-Vy : -195v
VSC : 145v
Zbias : 115v

I think that is the way LG stickers are formatted anyway

[pilotguy251]

Re: LG 42PJ350-UB won't power on all the way?

Wow, that's interesting. Didn't see that at first. Well it looks as if they want to reach those, some do, but it clicks back off before the voltages stabilize.