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LCD monitor power problem

Paul Harisson

Dec 9, 2017
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Hello all, I have a Benq lcd monitor model no. RL2240h, which is not turning on from yesterday. When I turn on the power supply the amber power led turns on for a second and fades off immediately. I checked the capacitors and nothing was bulged out or broken. Can anyone help me out. Thanks
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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I would still recommend replacing the electrolytics filtering the output of the low voltage rails.

Caps can fail with no obvious symptoms, and I have repaired so many monitors this way (many with no obvious indications) that I just do it routinely.
 

Paul Harisson

Dec 9, 2017
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37EC9746-96CF-40F6-A2FA-7EDA2E2F5A4A.jpeg 33B86808-4DA8-4D93-A248-A67884891B3F.jpeg Do I need to replace all the electrolytic caps? I have attached the circuit board for your reference
 

(*steve*)

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I'd start with the three brown ones. I assume they're rated as 25V to 35V.

At the same time you could replace the four smaller black ones.

The large green one should be OK.
 

Paul Harisson

Dec 9, 2017
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I'd start with the three brown ones. I assume they're rated as 25V to 35V.

At the same time you could replace the four smaller black ones.

The large green one should be OK.
Thank u Steve. Yes they are 35v. The multimeter which Iam having doesn’t got capacitance tester. How do I test the defect in the caps which I removed.

Could I replace the 330mf 35v cap with 330mf 63v
And 690mf 16v with 1000mf 25v?
 
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Paul Harisson

Dec 9, 2017
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Hi, can someone explain this? The monitor is not turning on when it is connected to the cpu through dvi cable. But when I connect it through HDMI to a laptop the display works fine. And after if I connect it to the cpu through dvi it still works. Would this be a capacitor issue or someother?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Have you checked that the cable and the computer are working correctly?

Try the monitor on a different computer with a different cable, and try a known good monitor using that cable and a known good cable. If you can, isolate the fault to a particular thing (computer, video cable, or monitor)
 

Paul Harisson

Dec 9, 2017
5
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Dec 9, 2017
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Have you checked that the cable and the computer are working correctly?

Try the monitor on a different computer with a different cable, and try a known good monitor using that cable and a known good cable. If you can, isolate the fault to a particular thing (computer, video cable, or monitor)
The monitor works fine when connected to a laptop through hdmi. But when connected to the desktop through the same hdmi cable its not working.

But once the monitor turned on( through laptop-hdmi ) it works fine with desktop. So every morning I have to connect the monitor first to the laptop and once the monitor turned on I connect it to the desktop.

What is the cause for this issue? Is it because the desktop not providing sufficient power to the monitor as the laptop gives?

FYI I only replaced the three black caps. The brown ones were still there.
 
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