42LG50 no backlight

[torpex505]

Re: 42LG50 no backlight

ok, I disconnected the ribbon that connected the inverter to the T-con board, there was still no light after powering on. I reconnected that ribbon cable and disconnected the harness that connected the T-con board from the I/O board, still nothing. I then left the harness disconnected and disconnected the ribbon cable from the main inverter again, and still no light.

[tommyjaxx]

Re: 42LG50 no backlight

Torpex, im going thru the exact same thing......exact same TV same. I have no new info to offer as of yet but I am right there with you, tryingto figure this bugger out.

[torpex505]

Re: 42LG50 no backlight

Sorry to hear that you're having the same problems. Let us know what you find out with yours. I've lost patience with mine. I'll pull it back out in a few weeks to start looking at it some more. Good luck.

[dietzcj]

Re: 42LG50 no backlight

Torpex and tommyjaxx ,
I have an LG 42lg50-ua as well that I am troubleshooting.
When I plug it in, I get no flash on the backlights, but just the red flashing light at the power button.
I have also Unplugged both inverters, Same result (Red light flashing).
I have unplugged the T-con board, Same result (Red light flashing)
Unplugged both inverters, and T-con board, same result (Red light flashing).
There are no bad capacitors (Bulging or leaking). I have resoldered nearly all joints.

I have no problem ordering a new power board from ebay, but I just want to make sure I have isolated the part where the problem exists.

I think we can all solve this together.

[torpex505]

Re: 42LG50 no backlight

Torpex and tommyjaxx ,
I have an LG 42lg50-ua as well that I am troubleshooting.
When I plug it in, I get no flash on the backlights, but just the red flashing light at the power button.
I have also Unplugged both inverters, Same result (Red light flashing).
I have unplugged the T-con board, Same result (Red light flashing)
Unplugged both inverters, and T-con board, same result (Red light flashing).
There are no bad capacitors (Bulging or leaking). I have resoldered nearly all joints.

I have no problem ordering a new power board from ebay, but I just want to make sure I have isolated the part where the problem exists.

I think we can all solve this together.

Hi dietzcj,

I'm not too sure about this, but I think the red light would be an indication of a power problem(or possibly one of the inverters). The light on mine is blue when on and red when off (if I remember correctly.) Which I believe indicates that the TV thinks it's functioning correctly.

The backlight does not flicker on mine either, they just don't come on at all. Have you put a flashlight to the screen to see if you have picture?

[dietzcj]

Re: 42LG50 no backlight

As soon as I plug in the power cord the red light starts flashing.
I have not done that flash light thing so I will try that when I get home.

[dietzcj]

Re: 42LG50 no backlight

Would it seem logical that the problem exists on the power board if I do not have either converter plugged in and I get the same result ?

[dietzcj]

Re: 42LG50 no backlight

If it helps I have the service manual for the LG 42lg50.

[Dgtech]

Re: 42LG50 no backlight

If there is any flashing LED indicators on either of your sets, I'd specify the rate in which they are flashing. Many sets have various meanings for what each flashing code indicates. It will point out your problem sometimes. Posting pictures of the power board and the whole set layout (opened) would help a great deal as well.

[mbates14]

Re: 42LG50 no backlight

This looks like the same setup as the magnovox inverters I have worked on. in my experience, they either produce no backlight, or maybe a flicker of a backlight before going out.

its almost ALWAYS due to a faulty transformer. you MUST pull all transformers, one at a time, and do a resistance check on all windings. keep a chart. youll find a bad one.

[dietzcj]

Re: 42LG50 no backlight

@torpexx:
No pitcure with the flash light test.
The red light flashing is a simple 2 second fade on and off

Did you read my previous post with the statements where I unplugged both Master and Slave inverters ? I unplugged them both and then connect to power and I get the same result. i did the same with the T-con card.

I will post photos once my camera is done charging.

[Dgtech]

Re: 42LG50 no backlight

@torpexx:
The red light flashing is a simple 2 second fade on and off

Try to find out what this code means. This will give you a clue 99 percent of the time. Look for a service manual. They should tell you what this means and how to fix it.

[dietzcj]

Re: 42LG50 no backlight

here are the pics

[dietzcj]

Re: 42LG50 no backlight

dgtech, I posted the service manual above. I would like to know what that code means, it is not really posted in any service manual or LG support.
I have a phone number to an LG service repair tech who should know the answer.
Thanks for all the comments.

[dietzcj]

Re: 42LG50 no backlight

Okay, so I talked with my LG guy in Virginia and he says that the red flashing lights means that the unit is going directly to "Standby" and not even making an effort to power up the inverters.
THis is confirmed since I unplugged both inverters in my initial testing.
He said that capacitors are usually the cause on these power supply boards (from what they have serviced). I do not see any that are bulging or leaking but that may not always be the case with bad capcitors.
I will take each one out and test with my multimeter.
Worst case I can just replace them all (9 of them) and see what happens.

He definitely thinks it is the power supply though.
I will post my finidings here later tonight.

[Scenic]

Re: 42LG50 no backlight

the caps look like they're Sam Young -> replace on sight (all of them, except the big 400+V one)

[dietzcj]

Re: 42LG50 no backlight

@Scenic: what do you mean by "Sam Young" ???

[Scenic]

Re: 42LG50 no backlight

the manufacturer of those crappy capacitors on that PSU board..
http://www.samyoung.co.kr

[torpex505]

Re: 42LG50 no backlight

Sorry, I had a busy weekend moving the ex out. It seems like you're on the right track. I've been looking everywhere for that manual, so thanks for posting it. I'll try to look it over tonight.

[dietzcj]

Re: 42LG50 no backlight

Well, I ended up just buying an entire power supply card from ebay for $30. When I get it and install, I will post results here.