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!

[Samuel_Sung]

I believe the splitter I linked to negotiates the resolution with the different monitors/TV's connected.

It's worth a shot trying yours but I can't say any splitter will work for certain, it was merely an idea that may be worth trying. 

Another temporary workaround would be to setup a screensaver and select "Blank." This is what I was doing before and it blacked out all my monitors, which was more tolerable. 

[msimmons99]

It does sound like the one you pointed to is more likely to help (if any will). Mine is a switch that I don't does any negotiating. It's worth a try.

I never even thought about the blank screensaver idea. Good idea. It will keep the monitors from sleeping and saving energy but use should be minimal.

Thanks!

[BenignCosmicEntity]

Seems like this is an established problem with Samsung monitors across multiple models, so that sucks. For those tracking this issue, this is happening on my Viewfinity 34 inch (S34C502GAN) with an M2 MacBook Pro 14” connected using DisplayPort from a usb c dock. I have multiple other connection methods at my disposal, so will update when I’ve experimented a bit. However, the real fix is probably a firmware update from Samsung, and it’s disappointing to see there’s no response from them here confirming the issue.

[BenignCosmicEntity]

Can confirm the issue appears to be either with DisplayPort on the monitor or some DP specific technology in my case.

I tried the following connection methods:

1. DP (dock) to DP (monitor)

2. HDMI (dock) to HDMI (monitor)

3. DP (dock) to HDMI (monitor) via AmazonBasics converter cable

I only observed the sleep mode loop on first configuration.

[msimmons99]

In my case it is HDMI > HDMI.

[BenignCosmicEntity]

So I continued trying a few things. I swapped out my MacBook for a windows laptop (2018 HP Elitebook x360), and tried my various cable options again. It works the same as the MacBook, with DP > DP connection being the only one with the sleep loop issue.

However, as I was connecting things up I noticed something else. My HP laptop battery was completely drained and wouldn’t power on initially, but the monitor started cycling through no signal/sleep as soon as it was connected. Note it stops cycling when the dock is disconnected from a computer.

So at the very least that confirms this issue cannot be fixed through any OS-specific power settings, but also is rather confusing. If not the computer, what on earth is reviving the signal on the monitor?

So now I’ve tried a few really stupid things. Back with my MacBook since it’s not OS specific, I connected the computer through a non-thunderbolt USB-C cable that cannot carry display information. This triggered the sleep loop on the monitor.

Then I tried plugging a normal USB-C to Lightning cable into the thunderbolt port on the dock and didn’t put a device on the other end, and the loop started on the monitor again.

So here’s my slightly educated hypothesis: With very little knowledge about how DP and HDMI actually work, but moderate knowledge about electricity and some other digital standards, I think the monitor’s own signal is getting reflected back at it and the firmware is too stupid to figure out it’s talking to itself. The monitor probably sends out a signal every few seconds to check if there’s a device on the other end. When that signal reaches the terminus (computer, or end of a lightning cable I guess), depending on the hardware, natural resistance in the setup, type of cable or whatever other situation, it gets bounced back and the monitor thinks it’s something, but it gets no actual data and goes straight to sleep… until it pulses out another check.

Tldr: nobody but Samsung can fix this issue, and I suspect they won’t on current models, but some iteration of their firmware down the line probably will

[msimmons99]

That's really interesting information. Thanks for doing all that testing! Not that I can do anything with it but I would hope Samsung would at least admit the problem and fix it.

FYI, I'm using HDMI to HDMI on a Win10 machine. So it's not DP but if it is something happening with the cable terminus (how that might happen is beyond me) I wonder if the cable plays a part. I will look for an older HDMI 1 cable in my spare parts and see if that does the same thing. I can try other connection types, too.

[BenignCosmicEntity]

I think it’s particularly telling that I could reproduce the issue without connecting any device through the dock. Changing any component in your setup including cable, hdmi switch, etc. could have an impact. For instance I’d be surprised if my DP to HDMI cable allowed the problem to occur since it’s a one-way converter cable. I don’t know enough to suggest an actual solution, so good luck finding something that works with your machine!

[msimmons99]

Yes. I think I'll try a few things. If a converter solves the problem as you say (not that that's necessarily a desirable solution) it would be in line with the suggestion of using a splitter made earlier. Maybe. If I learn anything I'll report back here.

[DragonHeo]

Hello all,

I’m having the same power problem with my 34” monitor. The connector is USB-C converter to DP port on monitor. So  looks like with DP, you can boost the refresh rate highest, but will be a problem with the idle power won’t stay off.