LG 50PT350 Help

[Bobabrett]

Really stumped on this one. When TV is turned on I get cable for about 3 seconds and then the screen goes black but audio continues. When I change to a different video source like HDMI 2, EXT, etc the menu comes up and even the screen saver comes on. I just can't get any picture on cable or even if I hook up a gaming console, that won't come on.

Took off the back, no blown capacitors or anything. I have a Multimeter at my office, just not at home, wanted to talk through the problem before I go looking for ohm readings.

any ideas what it could be?

[tom66]

Re: LG 50PT350 Help

Have you tried enabling the EXT AUTO GEN on the control board? Pictures of the boards would help.

[Bobabrett]

Re: LG 50PT350 Help

Hi Tom,

I have not tried enabling the EXT AUTO GEN on the control board. How do I do that and what will it do?

Below are photos of the boards. Thank you in advance.

[tom66]

Re: LG 50PT350 Help

I require a closer shot of this board.
http://paperthinmedia.com/download/e.../image(2).jpeg

Then a small piece of wire can be used to turn on the auto pattern generator.

[Bobabrett]

Re: LG 50PT350 Help

Tom,

I've attached a closer image of this board. Let me know if this will suffice

Thank you.

[tom66]

Re: LG 50PT350 Help

OK, see the hole marked EXT_AUTO_GEN, and just to the right of it, under some tape, the other hole? Peel back the tape slightly, take a small piece of wire, and connect these points. Then remove the right hand cable going between the control and main boards. Turn the TV on and you should get cycling test patterns - do you?

[Bobabrett]

Re: LG 50PT350 Help

Tom,

I followed your instructions and got a blank screen. The backlights looked like they were on but nothing came on the screen. To very I did this correctly I included a photo.



Thanks!

[tom66]

Re: LG 50PT350 Help

It might be a good idea to try soldering the jumper in place quickly, it can be hard to make sure it is making connection.

[Bobabrett]

Re: LG 50PT350 Help

Tom,

finally had a chance and got a new piece of wire and soldered it in a bit. Got something new this time. When I turned it on, the TV screen went all blue and then shut itself off after a few seconds.

[tom66]

Re: LG 50PT350 Help

OK, that means we have to do one last thing, the main board appears to be turning off the TV. The connector between the main board and power board. Please remove this from the main board end and locate the pins AUTO_GND and GND. Connect these pins together with a wire. Then turn TV on, the patterns should cycle indefinitely, do they?

[Bobabrett]

Re: LG 50PT350 Help

You might have lost me here.. do you have an example of this, or is there an easier way?

Thanks again Tom.

[tom66]

Re: LG 50PT350 Help

There should be a label next to the connector on the power board, is there?

SM http://servicemanuals.pro/serviceman.../download.html

[Bobabrett]

Re: LG 50PT350 Help

Is this the one you speak of? If yes, how do I connect them?




Thanks again for your help.

[tom66]

Re: LG 50PT350 Help

Correction, you should just be able to leave that connector unplugged and TV will turn on automatically. then it should go through the test patterns. If it does not you have a control board or power board issue.

[Bobabrett]

Re: LG 50PT350 Help

When the jumper cable is connected to the EXT_AUTO_GEN and to hole on the right of it and that cable is unplugged, I get a blue screen and it immediately shuts off. So, if that means I have a control board or power issue, is there a way I can tell which one? Would I be able to use my Multimeter on the power board to find the culprit or at least narrow it down?

[tom66]

Re: LG 50PT350 Help

Yes - can you use your multimeter to check the Vs and Va test points on the power supply - I think they are the wire links marked VS_TP and VA_TP.

Use DC volts, highest scale. Red probe on test point, black probe on the chassis.

They should be about 200V & 60V, exact rating printed on the plasma panel's model label (marked LG Electronics PDP50T1##### Made in <Country>... this is different from the TV's 50PT350 model number.)

[Bobabrett]

Re: LG 50PT350 Help

OK--I know it's been months since I posted about this but I've been traveling and working on the TV as a side project. I replaced the logic board on the TV and I got excited--I turned it on and TV started playing---for about 5 minutes and then the screen went out again. I turned it off and turned it back on and I got a blank screen. I then turned the TV off for 1 minute, turned it back on and once again the TV worked for 5 minutes before the screen going blank (still audio from the station).

Please help!

[mmartell]

Re: LG 50PT350 Help

Sounds like you got a bad logic board. Try spraying a little cool air over it from a duster can and see if pic comes back on.

And make sure all cables/ribbons are seated properly.

[Bobabrett]

Re: LG 50PT350 Help

I really don't think it's the logic board since I just replaced that part and it's basically doing what it was doing before. Other thoughts on what it could be?

[mmartell]

Re: LG 50PT350 Help

Have you done what tom66 suggested in post #16 ? Take voltage readings when you have a pic and again when it goes out. Sounds like a voltage could be dropping out due to cold solder joint or component being flaky when heating up. I still recommend using a duster can to cool down components just not sure where lol. If you find a suspect voltage that will narrow down the location.