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Old 01-16-2019, 10:27 AM   #1
ibanix
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Default Pa238qr

Greeting fellow badcaps friends!

I've got an ASUS PA238QR with issues. The monitor front panel LED turns on; and the backlight turns on; but then both turn off after a few seconds. No input shows, no OSD menu.

After taking the monitor apart, visual inspection of the capacitors showed nothing abnormal. All caps and other components on both the switched-mode power supply and logic board look fine. I checked capacitance with a multimeter, and all of them look fine. I also checked the resistors, diodes and fuses while I was at it, and those are fine.

When powered up, the switched-mode power supply shows 5.2v on the 5.0v output pins... but 16.2v on the (indicated) 14.5v pins. I'm wondering if overvoltage is my issue here, and if so where the culprit lies.

Any suggestions?

Thanks in advance.
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Old 01-23-2019, 10:43 PM   #2
momaka
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Default Re: Pa238qr

Quote:
Originally Posted by ibanix View Post
When powered up, the switched-mode power supply shows 5.2v on the 5.0v output pins... but 16.2v on the (indicated) 14.5v pins. I'm wondering if overvoltage is my issue here, and if so where the culprit lies.
No, this is fairly normal. Most monitor power supplies with two rails typically only regulate their 5V rail and the other (usually higher voltage) rail is left unregulated. Last month, for example, I was working on a Westinghouse monitor that had its 13V rail peaking as high as 22V when the backlights were not running and around 16-17 when they were.

Quote:
Originally Posted by ibanix View Post
Any suggestions?
Post some pictures of the power supply and video/logic boards here. Caps don't have to look bad to be out of spec. Even measuring their capacitance won't necessarily tell you if they are good or not - you need an ESR meter for that.

Given that your power supply voltages appear to be up and running at least, I'd be more inclined to thing that the logic board may have bad caps or possibly a bad regulator.

That said, if you connect a running computer to the monitor so that it is sending an image to it, do you get a picture on the screen of the monitor when the backlights and LED turn On briefly? Or is there nothing ever displayed?
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