LG W2243S close to dead...

[Teodule]

Hi guys

I have this time a nearly dead LGW2243S monitor on my desk. I also got it from the local dump (it is my supermarket!!!). The monitor started a splash screen in japanese for 2 seconds and returned to standby.
First symptom was a smoky smell. I have opened the case and reconnected the mains. The guilty capacitor is C515. Now the screen does not even show the splash screen, it tries to light up the CCFL for half a second and returns to standby. CCFL Transformer seems to be OK. Fuses are OK. Chemical caps look prima facie OK. I have the service manual from a previous thread about the same monitor but it doesn't help me right now.


No ideas so far. Do you have a guess?

Any suggestion is welcome. Thank you

[budm]

Re: LG W2243S close to dead...

We need good clear pictures of the boards (top and bottom sides of the board)

[Teodule]

Re: LG W2243S close to dead...

There are pretty good pictures of a similar monitor in the following posting:
https://www.badcaps.net/forum/showthread.php?t=34868

I'll make a closeup picture of the smoking capacitor C515 ("N3 3KV SEC") although there isn't much to see. I will add the top and bottom side of the power supply board. I don't believe that the tiny data processing board has anything to do with the problem.

I have downloaded the service manual from the previous posting. Unfortunately the schematics appear to refer to another board (different references, for instance no capacitor C515)

[Teodule]

Re: LG W2243S close to dead...

Here are my pictures. I'll keep you informed of the progression...

[jetadm123]

Re: LG W2243S close to dead...

N3 3KV is a 3pf 3kv ceramic capacitor. Try measuring the resistance across it to see if it's shorted.

[Agent24]

Re: LG W2243S close to dead...

Replace the capacitor.

[Teodule]

Re: LG W2243S close to dead...

No C515 is not shorted. I have tried the inverter test with an 11W CFL lamp and nothing happens not the faintest photon from the CFL tube. Secondary winding resistance for the inverter transformer is 765 ohm. Transformer seems to be OK.

[Agent24]

Re: LG W2243S close to dead...

If the capacitor has smoked then it is damaged. It may have shorted, then burnt, and is now open circuit.

You still need to replace it. Good components don't emit smoke.

[jetadm123]

Re: LG W2243S close to dead...

Did you actually see C515 smoke? If yes, then replace it as suggested by Agent24. You'll have a very tough time finding a 3pf 3kv cap. Also, check the two large mosfets mounted on the vertical board (next to the inverter transformer) for shorts.

[Agent24]

Re: LG W2243S close to dead...

Finding a replacement capacitor would not be that hard... RS Components or Farnell should have them, if not there's always eBay eg: http://www.ebay.com/itm/25pc-Ceramic...-/130996084471

[mxslick]

Re: LG W2243S close to dead...

Look closely at the underside of the board in the area of the cap (lower left part of the full size pic, near the word "Danger") you can see a burned spot on or near the traces. :



There's either some junk on the board that is causing a short, or something leading off that trace which is shorted.

[Teodule]

Re: LG W2243S close to dead...

Thanks a lot or your replies.
@ mxslick: it looks as if you had taken a picture of my board :-) . Actually C515 smoked "gently" not much, but you are right, Agent24, good components don't smoke'. Thus I need to find a replacement. May be I can get one from another "donor" monitor or I'll by one at Conrads as soon as I am back home in Munich. There is very little chance to get one in the place I an now.

I guess the MOSFETs on the additional board are U501 and u502. Do you think a shorted C515 killed the MOSFETs?

I have connected the the boards (not the panel) and powered them. There is a faint start of the lamos and simultaneously I hear one tick coming from the power and inverter board.

Have a nice Easter Sunday.

[Agent24]

Re: LG W2243S close to dead...

That is your board

I did not notice the burnt area that mxslick did, as the attachments were downloading very slowly the other day, and I must have given up.

He is right, C515 may be fine, you may just have had burnt glue or some other stuff on the PCB. Scrape the burnt area and clean off any carbon as it's conductive and may be causing the problems.

[Teodule]

Re: LG W2243S close to dead...

Uhhh Well C515 is to be changed anyway because of his smoking capacity....I will clean indeed the area from possibly conductive (carbon) traces. I have also removed the white glue on the components side as it is known for becoming conductive when aging.

Does anyone have the actual schematics for this monitor ? The service manual exhibits obviously a different revision than the one I have).

[Agent24]

Re: LG W2243S close to dead...

Finding the schematics can be a pain. The PSUs in LCD monitors are usually supplied by a different company, so the schematics can be hard to track down.

If you search the PSU model number, you may find other LCDs that it was used in, then download their manuals and see if they have the PSU schematic.

[Teodule]

Re: LG W2243S close to dead...

I wanted to thank you guys. 3 years later. I took the monitor out of the basement....ans started from the scratch the repair procedure. Then I discovered my own thread.
I have cleaned the carbon residues and I have now the following behaviour: Splash screen (LG) appears. The inverter transformer whistles faintly A vertical part of the display (20 %) is not properly addressed (no image, vertical lines). Splash screen disappears after 2 seconds then a black screen. 5 seconds later there are 2 horizontal lines of look like smileys dancing in the middle of the screen for about 2 seconds. Then blank screen.
I connect now the VGA input to my laptop. The latter doesn't recognise the monitor as plug-and-play. No image is displayed. Now the red power LED blinks slowly.
I will post tomorrow pictures and, if possible a short video of the phenomenon.

[Teodule]

Re: LG W2243S close to dead...

And this is the end of the story: one of the CCFL is dead , one end is black and broken, see attached picture, therefore the 2 seconds to blank. If I find a replacement I'll give it a try. But the CCFLs break just by looking at them....