Mac Mini will not resume HDMI connected display...

[Koldov]

Hi All,

 

Just recently started using the Mac Mini a little more than usual (sitting in a cupboard gathering dust) due to getting some new iPads.

 

As it's HDMI and we don't have any HDMI native monitors spare for it, I've used it headless and used VNC to remote in.

 

To set up the iPads we use a sync trolley and configurator on the Mac Mini, so I pull it from the server room and take it and the trolley to my office.

 

This seemed to work fine and I guess the issue isn't a game changer, but during the last session I upgraded to Sierra.

 

There seemed to be a problem for a while after as I couldn't VNC in, I tried to set it up with a HDMI/VGA convertor, but no joy.

 

Thinking it was the connection at fault, I had to switch off the Mac Mini (!) and I took it back to server room that has an HDMI monitor.

 

I hooked it all up and switched it on and thankfully everything came back to life, but later on I went back in to find the monitor showing 'no signal' and nothing I did appeared to wake it up.

 

After much trial and error, it appears the Mac will not wake the monitor up - it doesn't matter which way round or what goes to sleep first either. If the Mac goes to sleep then although it wakes up (as I can remote in) it will not signal the monitor to wake up, similarly if the monitor goes to sleep and the Mac hasn't, nothing I do on the Mac wakes it up. This means that as it is a monitor for 3 servers (2 Windows which work fine and a Mac) that when the Windows Servers let the monitor go to sleep the Mac cannot wake it! I set all the 'no sleep' options I could for the Mac, but it means having it run a screensaver and remembering to leave it on the HDMI channel...

 

It appears that a quick Goooogle has hundreds of people with the same issue especially with HDMI and the Mac Mini, going back to at least 2012, but no actual solution.

 

Does anyone else have this problem?

Edited October 7, 2016 by Koldov

[Brimstone]

Is the Mac Mini connected using a HDMI Cables or a DVI Adaptor cable, or HDMI direct...?

[Koldov]

HDMI -> HDMI direct cable. Tried a different one same result.

 

On one rare occasion the monitor did come up but it was washed out and mainly pink! Another occasion it almost came up there was some sort of noise from the monitor speakers and distortion on the screen and then 'no signal'.

 

I've also noticed now it is connected back up to the monitor when I VNC in, the screen I get randomly resizes every few seconds.

 

Also, it seems that once I have the log-in screen up and enter the password, the mountain screen disappears and a black screen appears but I have to enter the password again.

 

One thing I've noticed is that when there is truly 'no signal' the monitor flashes that up in a consistent pattern across the screen, however when the Mac is connected it does it for a few seconds, stops then starts again - almost like it's aware something is connected, but just isn't getting a proper signal.

Edited October 7, 2016 by Koldov

[Martyn_OIAM]

Try using a vga cable, via a Tunderbolt adaptor. I would think it has something to do with the screen display settings. Try using screen share, to 'dial' in and set the different screen resolutions/refresh rates.

[Arthur]

As it's HDMI and we don't have any HDMI native monitors spare for it, I've used it headless and used VNC to remote in.

To use you Mac mini headless you will need a display emulator like the ones below because if you don't have a monitor connected the GPU gets disabled.

 

https://headlessghost.com

https://www.amazon.co.uk/dp/B00FLZXGJ6/