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.
Happens to me as well. SAMSUNG S80A (LS27A800UNNXZA) with both a Mac mini M1 and a Mac mini Pro M2. it only happens using USB-C or DisplayPort. it does not happen using HDMI, which is not ideal because I lose some functionality when not using USB-C.
I have tried changing EVERY. SINGLE. OPTION in the monitor (e.g. auto turn off) as well as the energy options in the mac (e.g. wake on LAN) Nothing seems to work, the monitor keeps waking up.
I have the same type of issue with the SAMSUNG 34-Inch S34J550WQN (SJ55W) when trying to use the power plan settings to turn off my displays (without putting the computer to sleep).
This behavior also happens when restarting the computer, even during bios bootup (so it is not a Windows issue).
It's connected to an ASUS ROG Strix G16 through the HDMI port (using the Nvidia RTX 4060).
When the laptop turns off my displays, the monitor will flash HDMI1 three times before going to sleep for 4 seconds (blue light blinks one time) and then repeating the cycle. This happens when the computer turns off the screens due to power plan timeout and even when restarting the computer during bootup (pre-windows).
I believe the monitor is making the computer think the HDMI has been disconnected and then immediately reconnected when it loses signal because of the chime sound I sometimes hear accompanying this behavior, which is the same sound as disconnecting/connecting the HDMI cable.
I think the computer is somehow reacting to the HDMI disconnecting/reconnecting by polling the connection because it believes the HDMI has just been connected, which is then lighting up the monitor.
Furthermore, while the HDMI 1 flashes in the top-left corner of my monitor (and also when the flashing stops and the monitor turns off for 4 seconds), the monitor toggle button will be unresponsive and won't display the menu options.
I have 2 other monitors (Samsung S60UA and LG 24QP500-B) that do not exhibit this behavior when connected to the same HDMI port (Nvidia RTX 4060 dGPU).
The SJ55W monitor does not have this issue when connected to ASUS ROG Strix G16 via USB-C (Intel iGPU).
The SJ55W monitor does not have this issue on an ASUS TUF F15 via HDMI (Nvidia RTX 3060).
I have updated the Nvidia drivers;
changed the video source on the monitor (HDMI 2);
turn auto-scan inputs on/off.
Update: I replaced the laptop with an identical model (Asus ROG G16) and this time did not update the bios/drivers.
The replacement has not exhibited the same issue with the external monitor.
Are you using DisplayPort or HDMI? I have had this exact problem with a pair of Samsung U28E590 displays on a two display setup with a series of Macintosh computers connected via DisplayPort through a USB-C dock.
The displays power up through out the night for a few seconds, show a dark gray screen with the [DisplayPort] indicator in the upper left, and then go back to sleep. I've finally started turning the monitors off at night.
This has been going on since mid-2020. I started with a mismatched pair of one U28E590 and an older Monoprice monitor. In 2022 after my wife got a new display, I replaced the Monoprice with her old U28E590s so now I have two and they both do this.
I finally searched to see if I can find a solution to this and I found your post.
Mine is connected through HDMI.
Unfortunately, no response from Samsung. One person tried to help by contacting Samsung but couldn't get a response from them.
The forum seems to be where questions go to die.
Although it shouldn't have to come to this, perhaps a HDMI splitter would resolve your issue.
For the mac user, perhaps using a DP to HDMI cable would resolve your issue (additionally, you may also try using it with the splitter mentioned above). I was just using a black screen saver in lieu of having my monitor turn off. Otherwise, you may want to consider using a different USB-C dock.
That would send the same signal to both monitors. I'm using the two monitors for an extended display via the video card. The only way I can see using this is between the card and one monitor but I don't see how that would help with the monitor turning on and off.
Am I missing something?
My suggestion would involve using one splitter per monitor. The purpose of the splitter is to add an additional layer that takes over the hardware signals between the computer and monitor.
Oh, I see. Interesting idea. I have one Samsung monitor so I'd only need one splitter.
I have an HDMI switch I'm not using: https://www.amazon.com/Kinivo-Premium-5-Port-Switch-Remote/dp/B07CRWBPN4/
Would that do the same? I suppose it's just passing the signal through so maybe not. If not, I can try the splitter you suggest and report back. Yes, it shouldn't come to this but it's a cheap fix.
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.