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Released May 23rd 2017, and is a HDR capable 4K monitor from Dell, in their UltraSharp lineup.

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Dell U2718Q Monitor Keeps blacking out

I have a Dell 4k U2718Q that seems to have a problem with staying on. A few months ago it stopped turning on at all, and I tried the power drain by pulling the plug and holding the power button for a while. That didn't seem to fix it so I ordered a new power supply board. After replacing that it came right on and (I thought) worked fine, for about 10 minutes, then it powers off again.

I'll unplug it and do the power drain with the button and it comes back on, and will continue to do this about every 5-8 minutes, but always comes back. Any idea what the problem could be at this point? Would it be the main logic board, like a capacitor that could be bad? I can tell it's still getting power and doing something because the computer is still seeing the monitor in the display properties, and it'll come and go as you plug and remove the hdmi cable.

I've tried the easy things, different cables, different computers, updated drivers, all with the same results. And it is plugged in to a surge strip, if that makes any difference.

Thanks for any ideas!

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Hi @rmfisher321us

With the monitor turned on and showing a display which then blacks out, try shining a flashlight at an angle close to the screen and check if you can see any images at all on the screen.

They will be very faint if there are any, so trying this in a darkened room may help.

If you can see images then there's a backlight problem with the screen.

Since you have replaced the power board, open the monitor and look for a cable that runs from a board to the back of the screen.

I can't see any obvious looking ones in the ifixit Dell U2718Q Teardown guide, but normally with most displays there's a cable for the video (usually a ribbon cable) and on for the backlights (usually just wires)

That will tell you where the backlights strips are connected

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good call on the checking with a flashlight. So, messing with it tonight I found that when it goes dark there is no image there, so it's not a dead backlight. And before where I thought it was still on because the computer was still seeing it, well, after about 20 seconds after it goes dark the display disappears from the computer. (I'm using a laptop so it sees the second display). So it does appear to be a power issue of sorts. But, it always does come back when doing the power drain, so it's not a permanent problem.

I think there are 3 boards total in this monitor, the power supply, main board, and another one I don't know what. So since the power supply has been replaced, logic would say it's now something to do with the other two boards. Any ideas?

Thanks for all the help!

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@rmfisher321us

The teardown guide doesn't have really good images of the individual boards, but as you mentioned earlier look for faulty capacitors.

There's one shown in the image on Step.2 of the guide but I'm not sure which board it is on. It doesn't appear to be on the power board.

Also leave the back cover off and check if the problem occurs in case it is a heat related issue. Worth trying anyway.

by

alright, well I finally got a chance to get back to this, and it's definitely heat related. Took the back cover off, and put a fan on the back of it and it worked for as long as I wanted. I left the cover off and turned off the fan and although it seemed to work longer than before, it still eventually turned off again.

So I guess next step is to see if I can find what is over heating on the board to try to replace it.

Thanks for the help

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whoa, just after I typed this, it came back on by itself! It's never done that before, once it went out it would only come back on by draining the power and unplugging it. This time when it went out with the cover off I had just left it because I was doing other things and all of a sudden it came back on! So, I guess whatever heat issue it has it does seem to have the ability to rectify itself after things cool down.

I guess when the cover was on it never gave it a chance to cool down enough to start working again.

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@rmfisher321us you can further narrow that down by doing a few things. First thing I would do is to wait until it turns off. Then apply some freeze spray to cool down individual components /boards to at least get an idea which board has the components that overheat. Your monitor should come on once the components are cooled off. Spray it on MOSFETS etc. that are exposed since those do not like the heat very much and turn off. Of course, it can also be caused by using capacitors that are of lower quality and have a low temp threshold. Check the marking on the electrolytics and see what they are listed at. Anything below 105deg C should be replaced.

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It sounds like you have already ruled out most of the common external causes (HDMI cable, computer, drivers), and the fact that the computer still detects the monitor is an important clue.

Since replacing the power supply board fixed the issue temporarily, I would look closely at the power delivery section rather than the video input side.

A few things I would check:

The timing is interesting: it works for about 5–10 minutes and then shuts down.

That pattern often points to a component that fails after warming up, such as:

  • Aging capacitors
  • A failing power regulation component
  • A thermal protection issue
  • Poor connection or solder joint

When you unplug it and do a power drain, the monitor resets and works again until the fault returns.

2. Check whether the backlight is actually turning off

When the screen goes black:

  • Does the power LED on the monitor stay on?
  • Can you still see a faint image if you shine a flashlight at the screen?

If you can see a faint image, the main board may still be working and the issue may be related to the backlight power circuit.

If the monitor completely loses power, the power board or power delivery path becomes more likely.

3. Inspect connectors and replacement board compatibility

Since the power board was replaced, I would also verify:

  • Exact board part number
  • Connector seating
  • Any loose cables between power board and main board

A replacement board that is similar but not an exact match can sometimes create strange intermittent behavior.

4. Capacitors are possible, but not always the cause

Bad capacitors are common in older monitors, especially in power supply sections, but not every shutdown issue is caused by them.

Visual inspection helps:

  • Bulging tops
  • Leaking electrolyte
  • Burn marks
  • Discolored components

However, some failing capacitors look normal, so testing may be required.

One other thing: a surge strip usually isn't the first suspect unless other devices are also losing power. Since the monitor recovers after a power reset, the fault is more likely inside the monitor.

My next step would be checking whether the monitor is losing the backlight only or actually shutting down the power system.

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Hello, @powergeek2683

As what jayeff already said, all answers on topic to the fix is accepted, but you MUST make sure what answer the AI gives you will absolutely work, the first answer the AI will give isn't always correct or helpful, so please, make sure that the AI answers are checked by a real human being, and check with the community guidelines to see what you can do for AI answers.

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Ryan Fisher will be eternally grateful.
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