Monitor won't stay off in sleep mode

[msimmons99]

My 27" FT45 monitor (LF27T450FQNXGO) goes into sleep mode and wakes up when it's supposed to. But while in sleep mode it will repeatedly turn on for a few seconds and back off. Continuously and regularly maybe every 10 seconds. What's on the screen is just what it was when it went to sleep; nothing changes there.

What's turning it back on? I've been turning the power off to make it stop at night or it will do this all night.

Thanks!

[Hexadecimal]

Moreso it's not the quality control, it's the development team who is responsible. However if you are using an HDMI on PC, that may be why you're having that issue.

[Hexadecimal]

Adding on to this, the panel is awesome, I just wish the implementation software wise was better. I actually like that this has Tizen OS for watching content. But for everything else, I hate it; unlike the AW3423DW, there is no toggleable mode for either HDR 400 or 1000 modes, you just have to fish in the menu to find the Peak Brightness setting. Then you have to turn off and on the HDR on windows then you get the 1000 nit brightness on a 2% window.  Simply put, the team who develops the OSD settings and optimizations need to listen to the community more, I'm so glad it there is OTA updates and they they actually ARE listening to the community concerning some issues, but there needs to be more transparency. The team over at Dell who uses the same panel for the cheaper DWF model has no entirely fixed the weird HDR problems they were having and now has comparable quality; we need the same level of communication with the team responsible for doing the OSD / OS updates for this monitor. I believe and I hope that they will continue to fix issues, but I'd love it if there was more responses in this community concerning issues about what we as users face. Love the monitor it's amazing, just wish for a better line of communication for people on the team to see what we need solved.

[InsertPupil]

Same issue here. Tried different mDP to DP cables but still the same.

I contacted Samsung online support, they gave me a monitor driver file to manually update the monitor driver for Windows. However that doesn't help too.

If setting the refresh rate to 60Hz, issue will be gone. But if set to 120Hz or 175Hz, issue comes back.

I mentioned to Samsung support that I saw same report of issue in this Samsung forum, the support guy said "issue reported in forum cannot be validated" and simply disregarded your report here. What a joke!

They said will escalate my issue to Level 2 support, and come back to me.

Let's see what will happen, and I will update here if they can really solve this non-sense.

[Members_IaCDQLM]

I have both my T55 monitors set to 60Hz and still have the issue. I've also tried all the previous suggestions in this string as well.

I also wish the messages could be flagged w/ "solution" once identified.

[Wizardling]

Even if lowering refresh rate worked, I still wouldn't call that a solution. I bought a 75Hz display (F24T450FQE). I want 75Hz. Not 60.

I contacted Samsung support about this issue nine days ago, and still have not heard back about my case. Should invest any actual hope in this process? This is the first time I've contacted Samsung support.

[Wizardling]

I just had my new Samsung 24" T45F monitor delivered, and after going away and returning to my Windows 11 PC (which is set to sleep its screens after 20mins of inactivity) later this same day, I saw the T45F was turning its screen on every… seven or so seconds I guess, to unhelpfully inform me that it is connected to HDMI 1.

Absolutely bananas. What is the point of displaying a bank black screen with the input source every seven seconds while my PC is providing no signal because it has slept its screens? My LG 29UM69G-B monitor connected to the same PC remains off while the PC is sleeping its screens. Why isn't my new Samsung T45F doing the same?

The only difference between these two connected monitors is the LG is connected via my graphics card's DP port, and the Samsung is connected via the motherboard HDMI port to use my i5 8400's iGPU instead (intentionally - that's the way I want it). But until last weekend, I had an old Viewsonic monitor connected to my iGPU and it didn't turn its screen back on every seven seconds when the PC slept its screens.

So I'm forced to blame my new Samsung T45F 😞

[DR55]

I had the same issue (monitor flashing on and off when PC sleeps). Surface Laptop, HDMI from monitor (LU32R590CWNXZA) into mini DP port on surface dock. unplugged from surface dock and plugged directly into laptop mini DP port. Issue went away. 

[Exostenza]

Well, I just solved this for myself as I had the same problem of the monitor cycling off and on forever while the monitor was asleep and my PC was on - I have the Samsung G75T. All I did was plug the DP cable into the middle DP port of my RX 6800 XT and now the monitor stays asleep as it should. I have no idea why one port would display different behaviour than another but it works and I only use two monitors so I can use DP ports 2 and 3 instead of 1 and 2.

I get this won't help a lot of people who are experiencing this problem with only one DP port to use but for some of you try another port.

EDIT: Scratch that as it started happening again the next day...

[howardc64]

Found yet another sleep mode incompatibility on my Samsung 27" USB-C monitor (LS27A600UUNXGO) with Macbooks besides the auto wake up cycling behavior with USB-C cable.

HDMI connection with 2015 Macbook Pro will have faded colors and wrong resolution when MBP wake up with external kbd/mouse. Have to open/close lid to restore the image. MBP need to be in real sleep mode (maybe few min after putting it to sleep)

So this monitor basically can't be used with my M1 and Intel MBPs in both USB-C and HDMI connection.

[Wizengy]

I am seeing this exact problem on my system:
Monitor: Samsung UR59 32" 4K,  Desktop win10, new gigabyte AMD X670MB, old RX 5500 XT video card.
Running 2 monitors. Samsung monitor at 4k with DP cable.

Current solution: Black cloth cover that slides over monitor at night.  Cost: 30 minutes.

After reviewing 10 pages of diagnostics and trouble shooting, this seems the best solution for now.