Catalina black screen

[ShizPadoo]

I’ve searched for similar cases but I didn’t find any.
Just installed Catalina, didn’t have it hang on the progress bar but after that I assume it restarted and then the fan blasted for about a minute and then nothing happened. I have a black screen and my monitor light blinks.

I have switched off and on again but still a black screen. If I press any key on the keyboard I hear the speaker make a tone like a small drum but the screen doesn’t wake.
Latest Mac Mini. Any ideas what I can do?

 

[ShizPadoo]

I’ve tried all kinds of key combinations when powering on, with my wireless Logitech keyboard that is Mac compatible and a wired windows keyboard. Nothing gets the screen to show an image.

 

[Dave_O]

If you are using a TV over HDMI as a monitor, this is an issue that has been seen. See https://discussions.apple.com/thread/250715830?page=1

A USB-C to HDMI cable can be a workaround.

 

[ShizPadoo]

Thank you very much for your reply, but I have just resolved it and it's the most unusual thing I've ever experienced.

So, I have a wireless Logitech keyboard that is Mac-compatible and supports 3 devices. I Googled all kinds of key combinations for resetting SMC, PRAM/NVRAM and none of them worked. However, I could hear a tone when I pressed keys like Enter, Backspace etc, so I knew there was life in there somewhere.

I needed to do some jobs, so I left the Mini on in case the update was still working on th eupdate somehow, but when I returned nothing had changed. I got a wired Windows keyboard and tried all the key combos again, but still no good.

Then I decided to talk to Apple Support in a chat session and basically did the same things over again, which doesn't bother me because it's their job and they have procedures to follow.

The last thing they asked me to do was reset the SMC by unplugging the power cable for 15 seconds, plugging it back in for 5 secconds and switching on. I have done this repeatedly throughout the day with no success, but I did it anyway.

When it ultimately failed to solve the problem I decided that I would try another input on my monitor. Now, I have the Mac Mini, an Acer PC and a custom gaming PC plugged into HDMI1 (Mac), HDMI2 (Acer) and DP (Gaming PC). As the Acer uses HDMI I disconnected the cable from the back of the Acer to put in the Mac. When I did this, the Mac picture showed!!!

How unplugging a cable from a switched-off-device made it work I will never know.

 

[IowaLynn]

Last week people talked about HDMI issues, and unplugging any HDMI device until the system is fully installed, helped others. My HP monitor very basic but uses HDMI to USBC dock on my MacBook (2015) had an issue.

 

[ShizPadoo]

I only usually read the front page, so maybe I should spend more time in the forums ?

The only other thing I can think of is there being some kind of mega-coincidence that at the exact same time as I unplugged the HDMI cable, the SMC reset just finished.

Anyway, I have just returned from the shops with a USB HDD and a pen drive to make backups and bootable media in case worse happens in the future ?

 

[MiniMacDonald]

I’ve searched for similar cases but I didn’t find any.
Just installed Catalina, didn’t have it hang on the progress bar but after that I assume it restarted and then the fan blasted for about a minute and then nothing happened. I have a black screen and my monitor light blinks.

I have switched off and on again but still a black screen. If I press any key on the keyboard I hear the speaker make a tone like a small drum but the screen doesn’t wake.
Latest Mac Mini. Any ideas what I can do?

ShizPadoo, I had this same problem. My LG 4K monitor went black near the end of the OS upgrade. After an unsuccessful chat with an Apple tech, I decided to
1) shutdown my Mac mini from the power button and disconnect all my peripherals including the monitor.
2) reconnect the Mac mini to another video source (HDTV in my case) plus a keyboard and mouse.
3) finish OS upgrade.
4) delete all software drivers associated with the monitor that went black during the upgrade.
5) shutdown the Mac mini and disconnect it from the working video source.
6) reconnect the Mac mini to original monitor. (Keyboard and mouse too)
7) You should then have full video with your monitor. The only issue might be occasional monitor distortion and maybe a green band on one side.
8) contact the monitor vendor to get the latest update. Their update may not be authorized which will be confirmed by a screen message in Safari. In that case, the vendor needs to be notified that they do not have an authorized update if you need it.
Hopefully this works for you.

 

[ShizPadoo]

Thanks to everyone for the advice. It's working now, but I have several things to try if it happens again