LG 50PN6500 turns on, no signal or sound, goes to backlight

[asaflier]

First of all, thank you to everyone on this forum that devotes their time and experience to aid those of us who need the assistance.

That said, I fall in the latter group with a LG plasma tv purchased around 2012.

Both the TV and TIVO Roamio began problems simultaneously, I suspect the cable line may have played a role (with a storm), as it was recently re-routed past the surge protector by xfinity personnel.

Symptoms:
Red light on.

TV not responding to remote unless its unplugged for five minutes.

Upon plugging in, the backlight comes on, then the "no signal" display box appears on the screen - tried HDMI 1 & 2 with both the TIVO and a DVD player (that works on another TV), also tried the ANT line with a standard cable box that also works on another TV - "no signal" box shows on the screen with any of these combinations.

There is a short window of time after plugging the TV in that displays the "no signal" box (usually 1 or 2 minutes max) before it disappears and the backlight remains and subsequent remote commands are not received. As long as the "no signal" box is displayed the remote seems to operate the set.

No sound - obviously.

History: In 2013, just days out of warranty a storm took out the board pictured in the attached 1020 photo. Receipt said "Main PCB found shorted" P/N EBT62394206 was replaced.

I'm seeing that part in short supply, and where it's available carries about a $200 price. If that's what I need then fine, but if its just an inexpensive capacitor perhaps that could be replaced?

My experience: Very basic in electronics, former aircraft machinist - very heavy mechanical experience. I can follow instructions, have a digital multi meter but electrical is not a strong point.

I appreciate any help or suggestions you may offer. Thanks again for taking the time to read this.

[Hamie]

Re: LG 50PN6500 turns on, no signal or sound, goes to backlight

I'm afraid it does sound like main av board needs replaced again.

You can run test patterns on the set by connecting these 2 holes marked ext_auto_gen with a piece of wire.

you also need to unplug the LVDS cable going to the main av board (the flat cable that connects the control board to the main board)

Plug the TV back in and power on, if the test patterns run fine with no interruptions then you'll need to repair or replace the main board.

[Hamie]

Re: LG 50PN6500 turns on, no signal or sound, goes to backlight

[asaflier]

Re: LG 50PN6500 turns on, no signal or sound, goes to backlight

Thank you very much Hamie, for the directions and the close up!
I watched five full sets of test screens and presume I need the av board like you concluded.

These av boards seem to be scarce, absent on ebay, and most retailers are OOS but a few still have some for sale. This leads me to believe the av board is the more common part to fail in the TV.

I've located a repair shop nearby and will try them tomorrow morning, if they successfully repair it I hope to learn the components that failed, so I can determine if I need a standby av board, or a just handful of components.

Thank you again sir!

[Hamie]

Re: LG 50PN6500 turns on, no signal or sound, goes to backlight

It sounds like bad solder under the processor.
Do you have a heat gun?

[asaflier]

Re: LG 50PN6500 turns on, no signal or sound, goes to backlight

I do, it's adjustable between 200F - 1100F.
https://www.ryobitools.com/power-too...ts/details/281

The repair shop visit was unsuccessful, citing no way to test the board and lightning precludes them from attempting the TIVO diagnosis.

[Hamie]

Re: LG 50PN6500 turns on, no signal or sound, goes to backlight

You live in the U.S.
There is a company called Modus link, you send them your board and they repair it and send it back...

They get rave reviews from members on here.

Anyway you can try and reflow the mainboard first. Put your mainboard in the oven and bring it up to about 110-120 degrees Celsius.

Then give the main chip a good blast of the heat gun for 5-10 mins to completely reflow all the solder balls under the chip.

Careful not to knock the board or you'll ruin it.

Leave until it's cooled down then give it a try.

Might work, might not, it's free so worth a shot.

[asaflier]

Re: LG 50PN6500 turns on, no signal or sound, goes to backlight

Thanks for the tips, I emailed Modus Link and unfortunately they do not work on this board. I looked for similar companies with no luck.

I decided to purchase another one and learned they are more scarce than I thought. I found only on company in the U.S. but ended up purchasing from a Canadian company that appeared more professional. Should have it in a couple days, perhaps in time for the Silverstone F1 race.