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Old 01-03-2018, 07:49 AM   #1
_MsG_
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Default LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Hello,

I finally decided to register here as I wanted to improve my knowledge of electronics repair.

Someone gave me a LG Flatron W2243S-PF monitor which turns off after a few seconds and while it is on it makes a high frequency noise.

I already opened the thing and replaced some of the caps, but unfortunately still the same issue. I tried something else, and plugged out the upper CCFL connectors (one with red color wire and one with blue color wire).

With those two disabled the high pitch noise was gone, however the thing still turns off after a few seconds, exactly the same.

Later on I tried to also remove the bottom CCFL connectors (so no CCFL attached anymore) now the monitor does stay on, however you obviously don't have an image (I used a flash light, and then I see the screen still being on). With only the bottom CCFL connected the screen still goes off, but the red power led stays on.

Any directions with this specifics?

I added a picture of which cap I replaced. Later on I discovered that there was another cap, which I forgot. I still need to buy a component tester (something like M328) so I can actually measure the caps.
What I replaced:
3 X 50 V 270 µF (C818, C830, C839)
2 X 10 V 1000 µF (C819, C823)
1 X 16 V 470 µF (C820)
Attached Images
File Type: jpg IMG_20171228_230601.jpg (208.0 KB, 15 views)
File Type: jpg IMG_20171228_230606.jpg (279.9 KB, 10 views)
File Type: jpg IMG_20171228_230611.jpg (212.0 KB, 9 views)
File Type: jpg IMG_20171228_230615.jpg (140.2 KB, 10 views)
File Type: jpg IMG_20171228_231346.jpg (188.7 KB, 28 views)
File Type: jpg IMG_20171229_130334.jpg (224.2 KB, 12 views)
File Type: jpg IMG_20171229_130340.jpg (190.6 KB, 11 views)
File Type: jpg IMG_20160303_161927.jpg (169.5 KB, 27 views)
File Type: png Naamloos.png (1.00 MB, 22 views)
Attached Files
File Type: pdf W2243S.pdf (14.48 MB, 23 views)

Last edited by _MsG_; 01-03-2018 at 08:14 AM..
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Old 01-07-2018, 05:02 PM   #2
piernov
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Try to connect the 2 bottom CCFL on the top connector and check if the high pitch noise is still there. If it's not, the top CCFLs are probably the cause of your issue. If it's still present, I would guess the transformer is bad.
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Old 01-13-2018, 08:18 AM   #3
_MsG_
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

I think it must be something with the transformer, because I discovered that the initial issue it has is not that the display turns off, no only the backlight is turning off.

Is it likely that the big cap has degraded and not able to supply the voltage anymore? And I also forgot to replace the tiny cap you see just above the big heatsink.

I ordered a component tester so I can actually test caps instead of randomly replacing things. I'm a bit precautious because of the high voltages of the CCFL I read everywhere.
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Old 07-01-2018, 02:12 PM   #4
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Hello MsG,

did you solve your problems with this monitor? I have similar issues with the same model, but in my case the backlight is turned off after 0,5s. I did the same as you , I replaced the caps, it didn't help. CCFLs are OK as I have tested the unit with different CCFLs and the same problem arises. Thus the transformer is a good guess but not worth purchasing anew, I suppose.
Did you notice that the service manual you attached is for this model but refers to different electronic boards?What a mess !!!
I could't find appropriate schematics for this unit. Did you?
Cheers.
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Old 07-01-2018, 04:39 PM   #5
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

test how much current it is drawing from the wall
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Old 07-02-2018, 04:41 AM   #6
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Yes I had checked that. The unit draws about 6W when powered on. Not much I am afraid. I have read the 2 sec to blank scree post. I am afraid that the transformer might be bad. BTW I had started another topic for this issue. And many thanks for your answer.
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Old 07-02-2018, 08:06 AM   #7
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Hi,
I am making some progress. Voltages 5V and 28V are present at the output of the corresponding Schottky diodes. The primary winding of the CFFL transformer, has 0 ohms, measured on the board.That is bad. Either the transformer is dead or the driving circuit (the plugin board).....
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Old 07-02-2018, 04:06 PM   #8
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

End of the story: the PSU board is fine but one of thr CCFL is dead /broken, therefore the 2 seconds to blank. I'll try to get a replacement tomorrow at my favourite shop (the local dump)
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Old 07-02-2018, 04:27 PM   #9
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Quote:
Originally Posted by Teodule View Post
End of the story: the PSU board is fine but one of thr CCFL is dead /broken, therefore the 2 seconds to blank. I'll try to get a replacement tomorrow at my favourite shop (the local dump)
https://www.badcaps.net/forum/showpo...62&postcount=2
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Old 07-03-2018, 07:07 AM   #10
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

You could probably try converting this Monitor to a LED backlight system.
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Old 07-03-2018, 08:54 AM   #11
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

I would give it a try but I now see that 1/6 of the screen (right, vertically) is not properly addressed, no image and vertical lines. I guess either the TCON card or 1 of the connections to the LCD panel is defective. There is therefore not much to do with this unit. I will take the PSU put of it for the capacitors but that's all. My purpose was to identify the origin of the problem and I succeeded. But in this case the repair failed. No worry I still have a couple of candidates for repair in my basement!
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Old 07-03-2018, 09:03 AM   #12
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Always willing to help if you need it.
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Old 07-03-2018, 09:07 AM   #13
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Thanks Andrew. It is always a pleasure to discuss with competent and friendly persons. A bientôt!
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Old 07-03-2018, 09:15 AM   #14
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

You are most welcomed, my friend.
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Old 03-04-2020, 04:38 AM   #15
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Hello,
bios ?
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Old 05-28-2020, 05:10 AM   #16
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Default Re: LG Flatron W2243S-PF monitor shuts off after 3 seconds with high pitch noise

Took a while and I recently stumbled upon this repair again. Unfortunately I don't have the time currently, and besides that the screen is rather old, and relatively dangerous with the old ccfl backlighting. I am desoldering my new caps now and I'm going to hand in the screen to be scrap metal. If you want it you can take it. The screen itself is okay. I sometimes even get newer screens that take less of a hassle to get them fixed again Samsung SA300 series for example work again as new after only applying a simple firmware update.
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