Question Monitor won’t turn on after power outage

Jan 11, 2021
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Hello everyone! Two days ago my youngest kid tripped with the power cord of my UPS and my computer and two monitors shut down, everything turned on except one monitor, this have happened to me before with the same monitor, but after a couple of restarts and cable disconnect and connects, eventually the monitor would turn on, but this time it’s been a couple of days and the monitor won’t turn on, I opened the monitor to check the capacitors and they seemed to be ok, any idea of what could be the problem.
last time the monitor wouldn’t display any light on the power button, but when the computer restarted it turned on so I was thinking I could have something to do with the signal that wakes up the monitor, does that make sense?
Also the computer recognizes it as if it were powered on.
thanks for your help in advance.
my monitor is a dell U2312HMT
 

Aeacus

Glorious
Ambassador
so I was thinking I could have something to do with the signal that wakes up the monitor, does that make sense?
Just because power is delivered to the monitor and you'll see some life from it, doesn't mean that the display panel itself survived the blackout.

but this time it’s been a couple of days and the monitor won’t turn on
Electronics aren't biological living beings for them to "heal themselves" and start working once some days have passed. Electronics are like "on/off switch", either it works or it doesn't.

any idea of what could be the problem.
My best guess, the display panel itself has some circuitry fried, due to the sudden power loss.
Fix: buy a new monitor.
 
Sep 9, 2020
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Do you intend to try to repair the monitor?

What is your previous experience with electronics repairs?

At least take the cover off.
Sometimes (NOT always) a defective component can be identified with the naked eye.
 
Sep 9, 2020
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I am sorry.
I really missed it.

The next step is to measure the voltage inside the monitor. For starters, at least the ones that are small and safe.
For example, on the cable connector between the power supply and the main board.
 
Jan 11, 2021
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Just because power is delivered to the monitor and you'll see some life from it, doesn't mean that the display panel itself survived the blackout.



Electronics aren't biological living beings for them to "heal themselves" and start working once some days have passed. Electronics are like "on/off switch", either it works or it doesn't.



My best guess, the display panel itself has some circuitry fried, due to the sudden power loss.
Fix: buy a new monitor.
thanks for your input. i know that electronics are like an on / off switch, but as i said, i have had this happened before and after some tries and connect and disconenct everithing it turned on,

this time was the same thing, it turned on after a couple of days, but yesterday again i turned off everithing, disconected the monitor to arrange all the wires in the back of my desk and when i connected everything again, the monitor, again, wont turn on.
 

AlexTheFern

Upstanding
Jan 21, 2021
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Electronics aren't biological living beings for them to "heal themselves" and start working once some days have passed. Electronics are like "on/off switch", either it works or it doesn't.
one time my laptop fan broke and I put it there on my desk for a week, then I forgot it broke bc im dum and i opened it up and it worked fine. Didn't even notice it fixed itself till the next day.




But a month later it broke for good so theres that.
 
Jan 11, 2021
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ok, so i have another identical monitor and i switched the power boards and it still wont turn on, so its not the power board.
this have happened to many times and at the end it turn on again every time, some times it takes minutes, some times it takes days, its very random, i think ill start looking into the display board. thanks everyone.
 
Jan 11, 2021
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Update: ok, so the monitor is back! its on again, i connected it to a wall outlet without ground and voila! its on again, i dont know if that has something to do, but its working fine again,

My best guess, the display panel itself has some circuitry fried, due to the sudden power loss.
Fix: buy a new monitor.
i know that "buy a new monitor" is the easy advise but, the monitor works great, its turning on and off correctly every time i need it until it is disconected while its on, then it could take days for it to turn on, but once it's on, it has no problem at all! so what could be causing this?
 

Aeacus

Glorious
Ambassador
so what could be causing this?
Monitor has some form of PSU in it and it could be possible that once the capacitors are drained (when disconnected from the mains), it takes some time before capacitors are recharged (when connecting back to the mains), before monitor turns on.

I still advise getting a new monitor since it's clear that the blackout(s) you've suffered, has compromised the monitor and it is a fire hazard.

It's like when car has been in serious accident and rather than writing it off and scrapping it, it is fixed. Example video:

View: https://www.youtube.com/watch?v=2j2ydYItqQQ

While the car can be repaired and restored to the original appearance and functionality, would you still drive that car? Despite the metal having no structural protective strength in it? Sure, you can be fine as long as you won't end up in the crash. But if you do end up in a crash, the car will fold like accordion.
 

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