Power Management - What is keeping my computer awake?

[heinhuiz]

Hi there, I'm looking for some help.

I'm using Cinnamon on Mint 19, although my problem started earlier, on 18.3 (which is why I upgraded to 19 in the first place).

I used to have my screens (I'm on a two monitor system) to turn off and eventually the computer to suspend using Power Management. Since a few weeks, just after the screens turn off at the scheduled inactive time, within 3-5 seconds they turn on again, with all content from the secondary monitor moved to the primary screen. Obviously, the computer will not suspend either.

After upgrading to Mint 19 the problem is still there. On top of that, probably for the same reason, TLP does not turn off the screens nor lets it the computer go to sleep.

What I've done so far:

• Made sure wakeup for all devices is disabled;

• Closed all programs;

• Checked with system monitor that no process is using CPU;

• Wondered what else to do.

*) Only when the screens turn on again, process 'cinnamon' briefly uses 1% CPU. All other processes stay at 0%.

Any ideas? What can I check next?

[catweazel]

• Made sure wakeup for all devices is disabled;

Have you verified that wake on lan is not enabled in the BIOS?

[heinhuiz]

Yep. I've even disconnected the LAN cable to check if that would help.
And at this stage the computer is still awake, it is only the displays that have to be turned off. Like I said they do, but only for a few seconds.