LCD monitor power problem

[Paul Harisson]

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*)]

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]

Do I need to replace all the electrolytic caps? I have attached the circuit board for your reference

 

[(*steve*)]

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]

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?

 

[kellys_eye]

Yes to both capacitor replacement values.

Testing is done using an ESR meter - originally rarely used but now incorporated as 'standard' in many of the multi-test devices you can get on eBay these days:

https://www.ebay.co.uk/itm/LCD-Comp...285951&hash=item41cf5cf45f:g:8NMAAOSwRplZt4oE

 

[Paul Harisson]

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*)]

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]

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.