Mac mini with M1 chip and Big Sur HDMI signal ceases?

Here is an update:

Note: I have two minis with one Samsung tv/monitor

The minis are named mini15 and miniM1. The 'MBPII' referred to is a Macbook Pro on the

local ethernet network.

This query is regarding miniM1. I also had a chat session with Apple support and was

given the usual questions about cables, cable connects, reseting PRAM/NVRAM and

starting in safe mode. BUT....( notes taken as events transpired)

8/4/2021 @ 12:53 P.M. while executing update (on miniM1) the monitor lost signal and I am

not able to establish screen sharing from mini15. The power light is still on on miniM1. All the

network server listings have disappeared from mini15 finder window.

I was able to connect to screen sharing from MBPII and did have a network link to mini15.

I restarted mini15 and was able to reestablish a screen sharing connection to miniM1.

It appears to still be downloading the updates @ 1:25 P.M. That is about and hour.

Just for the **** of it I switch the HDMI channel back to MiniM1 and there is a screen.

So I can assume it was some issue with the network that was effecting mini15 (?).

@ 1:48 P.M. It was taking too long and the updates were all to apps I don't use on Mini M1.

So I quit app store. ( I hope half downloaded updates aren't hanging around).

The current speculation is that the HDMI signal loss was due to network and security issues

in the miniM1 system, seeing how it effected mini15 via screen sharing connection.

Mini15 is so named because I bought it new in 2015. It has High Sierra running on it.

I hope someone can follow up on this and have some help available regarding it for

future or existing similar issues with HDMI signal loss on Mini with M1 chip and/or Big Sur

JK

I probably have solved the HDMI signal issue:

In System Preferences -> Energy Saver -> Turn Display Off After ( time scale)

I had it set for about 15 minutes. So I set it to 'never'. With possibly two machines

running at the same time and only one monitor, I don't want one machine to shut

off its display. But for future reference, how would one turn the display back on

when it is attached to a third party monitor via HDMI? The presence of mouse

and/or keyboard activity? I have not had to deal with this specific issue before.

I hope this might be helpful to anyone who is hunting for a solution to a similar

issue.

JK

Thank you for the suggestion about contacting service.

JK

I have also turned on screen sharing on the M1 mini so if the

video signal ceases I can hook up to it via screen sharing from

the other mini and continue to work or shut it down.

JK