LG M2362DP Backlight problem

[ononos]

hello everyone!
As the title states i am an owner of an LG flatron M2362DP 23 inch monitor Tv. Since i currently use it as a tv i'm posting the problem on the "troubleshooting tvs and video sources" section.
I'm from Greece so English isn't my native language, so please forgive me for any mistakes i make. I have basic knowledge in electronics, and although i have a degree, many things have changed since i finished a 2 year coarse (over 30 years ago). Occasionally i repair easy stuff, mostly things that break at home like appliances.

So i decided to try to repair my broken TV which i use as a secondary one in the kitchen. Well the problem is that there is no backlight. The tv works, i have audio, and i can see an image on the screen if i use a flashlight on it. So the problem is the backlight. Upon opening the TV i discovered two boards, the main board and the psu - inverter board. So (correct me if i am wrong) the problem must me in the psu - inverter board, since none of the 4 ccfl lamps are working .

I managed to find and download the service manual of the tv but there are no schematics or troubleshooting for the psu - inverter board in it. I've measured with a multimeter the components on the inverter section of the board but did not find any shorts. I have tested the inverter transformer with a multimeter and the primary coil has close to zero resistance. I assume that is normal. The part number of the board is 3PAGC20009A-R and i include photos in this post.

I would very much appreciate it if someone could guide me through troubleshooting the board or if someone has encountered the same fault with this tv.

Thank you in advance

[ononos]

Re: LG M2362DP Backlight problem

I'm planning in forcing the ccfls to stay on just to see if anyone is faulty. In the picture of the connector I assume the "ON" means inverter on and the "DIM" controlls the inverter dimmer. Does anyone know what the "M/S" and "OLP" mean?

[lotas]

Re: LG M2362DP Backlight problem

"OLP" - overload protection

[ononos]

Re: LG M2362DP Backlight problem

Hi again
This is what i have done so far:
- replaced all the electrolytic capacitors - didn't work
- replaced the mosfets that drive the inverter (aop605) - didn't work
- took apart the screen and discovered a bad connection on one of the ccfls. I resolded the bad connection and the lamps work!

But know there is a white vertical line at the right part of the screen. I have measured both ends of the flat cable that connects the main board with the screen for continuity and it seems ok.
Also when i disconnect the flat cable the white line goes away - all i see is a black screen (the backlight stays on)

Could i have damaged the screen when i took it apart? Is there something wrong with the main board?

[lotas]

Re: LG M2362DP Backlight problem

You could tear, tear, or detach from the glass one of these cables, when you took it apart, put it back together.

[ononos]

Re: LG M2362DP Backlight problem

lotas thanks for the quick reply. i have inspected the cables, the seem ok.
Because i only took the backplate off, i'm worried ithat i may have damaged the other end of one of the plastic cables. How do they glue back on?

Here is a picture of the white line:

[nomoresonys]

Re: LG M2362DP Backlight problem

Inspect for damaged pins etc, clean and refit the cables, in case they are dirty or misaligned a little, if no luck prolly did damage something, look and see if one of the connecting tabs is where the line is, if you can get to it you can try putting a little pressure on the tab where the line is, see if the line changes any. If tv is fully assembled can try squeezing the bezel where the line is, NOT the screen, to see if line changes any, that worked sometimes in older tvs where a little squeeze would make the contact needed to get rid of a line, just a little test for tvs with lines before dis-assembly, if a bezel squeeze or a slight flex of the bezel changes a line then it could be a tab bond getting poor contact.

[lotas]

Re: LG M2362DP Backlight problem

Here, no cleaning and displacement of the lvds cable will not help, there is obvious damage to the cable going to the glass.

[ononos]

Re: LG M2362DP Backlight problem

Double checked, cleaned and aligned all the connections. No change. The white line isn't aligned with any of the tabs. Put pressure on all four of them - no change. Is it worth taking the screen apart again? Is this fixable?

[ononos]

Re: LG M2362DP Backlight problem

No luck with the bezel squeeze. Is this thing fixable?

[lotas]

Re: LG M2362DP Backlight problem

The white line will not coincide with the damaged cable, since there are only 4 of them and they are distributed over the entire screen, disassemble again and view under a magnifying glass.

[ononos]

Re: LG M2362DP Backlight problem

In case any of them has detached, how to repair them?

[nomoresonys]

Re: LG M2362DP Backlight problem

Picture isn't very clear, can't see any damage, are those screws holding the panel driver board? if so you may have tightened that one a bit too much where the line is, maybe try backing it off a little if it is.

[lotas]

Re: LG M2362DP Backlight problem

In case any of them has detached, how to repair them?

If you torn or peeled off the glass, then you can't restore it at home.

[ononos]

Re: LG M2362DP Backlight problem

Okay i,ve dismantled the screen again, inspected with a microscope and found no physical damage, no tears, no bents - nothing. I applied pressure to the tabs while the tv was on with no change. The white vertical line won't go away.
I'm thinking know on bying a new screen. Does anyone know if the samsung ltm23ht01 is compatible with my screen lg lm230wf1- tle1?
Will the samsung panel work with my tv? Have they compatible connectors?