How to fix my relatively new computer monitor?

Thread Starter

MagicalMotor

Joined Aug 18, 2021
2
Hi,

I bought this Viewsonic monitor (VX2478-4K-HD)only a year and nine months ago, so it is not an old monitor, but I did use it everyday and a lot of times, I left it on all day. Anyway, the monitor started having problems a few months ago, when I turned it on, it would take a while for the display to come on, so I stopped turning the monitor off, and put the monitor to sleep instead, and the problem went away for about two months, and then it started again a few weeks ago, after I put the monitor to sleep, it would take about 5 mins, and then 10 mins, and then 20 mins, and then 40 or 50 mins(taking increasingly long)….for the display to come on again. I thought there might be something to do with the dp cable, so a week ago, I turned off the monitor and changed the cable, and then after I turned it off, no matter how long I waited this time, the display wouldn’t come on again. I did some research online, and it seems that these are the common symptoms for failing capacitors, so I opened the monitor yesterday, but sadly, all capacitors seemed to look fine(right? Please see the pictures), I didn’t see any bulged capacitors, and in fact, everything looks shinny and new, so now I am not sure what the problem is.

Basically, when I turn the monitor on, the little led blue light is on, there is backlight, but no display, and the “no signal” message doesn’t appear as well.

Any ideas what's wrong with my monitor? how to fix it? Do I need to change the capacitors? Which capacitors should I change? How long do the monitor capacitors usually last? Which one is the fuse(I don't seem to see one on the power board)?

Thanks,


P.S I don't think this problem has anything to do with the power adapter, right? since there is backlight, should i try a different adapter ?

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zophas

Joined Jul 16, 2021
143
Capacitors can fail without showing any signs of failure. Have you done any testing on the board other than visual inspection? Do you have a DMM and a soldering iron? If your DMM can read capacitance then you could try lifting one lead of each capacitor and test it. Testing with both leads connected may give you false readings if you don't have a schematic. I'm not knowledgeable enough to suggest anything else.
 

drc_567

Joined Dec 29, 2008
1,156
The capacitors labeled 33 μF, 100 volts are at a higher voltage rating than is typically seen. It may be that a transient, turn-on voltage has damaged one of these capacitors over a period of time. So as far as a wild guess, shotgun approach, you might consider replacing those particular capacitors with an equivalent or higher voltage rating part. ... Just be certain to mark or identify the + and - orientation of the installed capacitors, so that the polarity is correct.
 

Thread Starter

MagicalMotor

Joined Aug 18, 2021
2
Capacitors can fail without showing any signs of failure. Have you done any testing on the board other than visual inspection? Do you have a DMM and a soldering iron? If your DMM can read capacitance then you could try lifting one lead of each capacitor and test it. Testing with both leads connected may give you false readings if you don't have a schematic. I'm not knowledgeable enough to suggest anything else.
Thank you for your reply. I am new to this, do you think a transistor tester would work without removing the capacitors from the board?
 

AlbertHall

Joined Jun 4, 2014
11,539
Are you really sure it is out of warranty (rules vary depending on your location)?
[edit] You must check this before you start any soldering and invalidate the warranty.
 

zophas

Joined Jul 16, 2021
143
@MagicalMotor I'm assuming that the monitor is no longer under warranty, else you would not have opened it, right? I have no idea what kind of transistor tester you have but I'm not sure if it can be used to test in situ capacitors. Any components that are in parallel to the capacitors will affect whatever reading you get. You need to see if the capacitors are shorted or open or if intact then if they are anywhere close to their stated capacitance value. You will need an instrument that can at least show you continuity. You could make something up for this but it's just as easy to buy a small multimeter. Not all multimeters can read capacitance but at the very least they can show continuity.

Edit: If you take the capacitors out make sure to put them back the same way (if good), all those caps are polarized (+/-).
 
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