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Old 01-21-2019, 03:58 AM   #1
123XYZ123
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Default LG Flatron w1934s only power button flashing every 2 seconds

I made a video of the whole problem so maybe it will explain it to you best https://youtu.be/iEHrll_xRao

However, I will write the problem here too.
Well, as the title says when I plug the power cable the power button on the display just goes on and off every 2 seconds without showing anything on the display. While it's that way I disconnected the screen cable (picture 1) and then after few seconds the screen goes white, back off again for a second and back white and then stays white (I suppose this means the back light is working fine?). After that I connect the screen cable back again and then the screen shows some lines until I press the screen cable down with my hand on different spots until I find the one which makes the screen show the "check signal cable" window going around, I put some tape to press it down and it stays that way. However, when I connect my laptop to the monitor the screen on monitor goes back to its first state, blank and only the power button flashing blue light every 2 seconds, or sometimes it doesn't go back to the first state but the LG logo shows up on monitor screen then after it the "power saving mode" window and the monitor screen goes off with the power button light orange and stays that way until I press the power button, then it goes off completely and then when I press it again it shows again the lg logo, power saving window and goes orange (as you can see on the video). Now back to the first state with the laptop connected to the monitor. While in that state, blinking power button on monitor every 2 seconds, I again disconnect the screen cable, screen goes white and then again connect it back, then the screen shows some lines again and I tried pressing the cable but all it does is being completely black or the lines show up when released, so no more "check signal cable" what makes sense because it's connected.

So I have no idea what could it be, the vga board of monitor, the screen cable, the long thin board of the screen where the screen cable is connected (excuse me for not knowing the name) or something else?


Thanks
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Old 01-21-2019, 06:25 AM   #2
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

I forgot to mention that I did take the monitor apart because at first I thought it might be some bad capacitors on the power board causing the leds not go on but they all looked fine and the leds were working fine with the screen cable was disconnected (wish I tried that first heh, took the whole monitor apart for nothing).
Also, maybe the sound might say something which you can hear on the video when I go closer to the boad.

Thanks again

Last edited by 123XYZ123; 01-21-2019 at 06:26 AM..
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Old 01-21-2019, 03:59 PM   #3
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

https://www.hardwareinsights.com/rep...-repair-itself

This seems to be the exact same problem as mine, just I'm not sure which exactly capacitor did he replace and did he replace anything else?
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Old 01-24-2019, 12:17 AM   #4
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

Quote:
Originally Posted by 123XYZ123 View Post
https://www.hardwareinsights.com/rep...-repair-itself

This seems to be the exact same problem as mine, just I'm not sure which exactly capacitor did he replace and did he replace anything else?
Start by posting clear pictures of the power supply and logic boards. It would really help to see what we are working with. If your power supply board has any Hermei -branded capacitors like the power supply in the above link, you should consider recapping the entire power supply board. (Though I will say that CapXon, Ltec, and a few others are equally garbage and the same recommendation applies to them.)

Sure the capacitors may not appear to be bad, but that doesn't mean that they aren't - a capacitor doesn't have to be bulged to be bad. And since there is no telling if the capacitors are the cause of the issue, you will just have to eliminate them as a possible cause. My experience with fixing monitors over the years is that cheap garbage capacitors will eventually go bad, no matter what. So it's best to replace them the first time around.
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Old 01-24-2019, 06:55 AM   #5
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

Replacing the whole power supply board is not really worth the monitor, its an older one. I don't have a capacitor tester nor the right replacement caps, only 2 of 8 i found but its a question do my replacement ones work either coz I took them from an old PSU. So i will probably have to get myself a caps tester and then see. For now I'm putting it aside.
Thanks for the help.
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Old 01-24-2019, 02:41 PM   #6
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

It is best just to replace all the caps as a set except the large main filter cap, no cap tester needed if you do that.
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Old 01-24-2019, 05:09 PM   #7
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

Quote:
Originally Posted by 123XYZ123 View Post
Replacing the whole power supply board is not really worth the monitor, its an older one.
I agree, and I didn't suggest that either. I said _recap_ the entire PSU board. From what I can see, that's 8 capacitors total. 9 if you count the big one, which typically doesn't need to be replaced... unless it's a CapXon.

Quote:
Originally Posted by 123XYZ123 View Post
I don't have a capacitor tester nor the right replacement caps, only 2 of 8 i found but its a question do my replacement ones work either coz I took them from an old PSU.
Well, if you replace questionable parts with questionable parts, then you're going to have a hard time figuring out what the problem is if the replacement caps don't solve the issue either. With new caps, at least you will know that's not the issue anymore and can then look into other areas.

Quote:
Originally Posted by 123XYZ123 View Post
So i will probably have to get myself a caps tester and then see.
That's good to hear. Even the cheap cap/component testers on eBay can be very useful for finding bad caps. Ever since I got mine a few years back, I've been finding that I have a lot more "marginal" caps in my used/pulls bin than I thought before.

Quote:
Originally Posted by budm View Post
It is best just to replace all the caps as a set except the large main filter cap, no cap tester needed if you do that.
I agree.
However, beware of CapXon, because as I've had the pleasure of finding out lately even their high-voltage caps tend to fail a lot more often than other brands. 2 weeks ago, I opened a no-name LCD monitor that I had recapped some years ago. It was still working fine but had weird shades of lines going through the screen. Th3_Uniqu3 here suggested to check on the big input cap and I did - sure enough it was leaking from one of its leads. This is the 3rd CapXon high voltage cap I see failed in a year's time.
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Old 01-24-2019, 09:07 PM   #8
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

Thanks a lot for the replies.
If I decide to go for new caps, should I buy exactly the same or should I look for something particularly?
I will probably order from China, so it's gonna take a while
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Old 01-24-2019, 10:27 PM   #9
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

It's OK to order your cap meter / tester from China (eBay, AliExpress, BangGood, Amazon, etc.)
... however, do NOT order caps from China. Most are either cheap junk that may or may not work even out of the bag. The few that look like Japanese caps are typically counterfeit (and usually re-sleeved junk).

For caps, it's generally safest to use Digikey, Mouser, or badcaps.net store (for Euroland and OZ readers, there are a few other alternatives as well.)

You don't necessarily have to match the caps exactly, but typically it's better if you do (and there will be less doubts about the new caps being part of the problem). With that said, match the capacitance and voltage rating exactly. The other specs you need to match are ESR and ripple current (RC): it's okay to use caps that have ESR lower than the current ones (within reason - typically up to 1.5x lower ESR is okay), and equal or higher-rated RC. To match ESR and ripple current, you need to find datasheets for the current caps you have (look up brand and series online), then find the capacitor you're replacing in the datasheet, and note its specs there. As for physical dimensions: it's okay to use smaller or larger cap, but if you use larger cap, make sure it will fit inside the monitor box.

And if you need help with any of the above (finding datasheets for your current caps and looking for replacements), then post the brand, series, voltage, capacitance, and dimensions (in mm) of the current capacitors you have.
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Old 01-25-2019, 03:37 AM   #10
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

Alright, thanks a lot.
Currently I'm a little busy but when I have some free time I will take it apart and write every cap down.
I'm from Europe where would be best and not so expensive to order from?
From the sites you mentioned only one ships, Mouser but the shipping costs are more expensive than my monitor lol
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Old 01-26-2019, 04:33 PM   #11
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Default Re: LG Flatron w1934s only power button flashing every 2 seconds

I don't know which one would be the cheapest place to where you are, but typically for Europe, the parts websites are Farnell/Newarc/Element14, RScomponents, and member Behemot here on the forums, who is based in CZ. Badcaps.net store also ships to Europe, but I haven't last checked what the shipping was at (may or may not be worth for your monitor.)
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