Resolved Upgraded to Catalina 10.15.3 - no image via HDMI

[djc6]

I upgraded from Mojave 10.14.6 to 10.15.3 today - everything seemed fine when the upgrade was done.

I then shutdown my mac mini and ever since, no picture on one of my LG 27UD58P-B 4K displays. I have one connected via HDMI, one connected via CableMatters USB-C to HDMI 2.0 cable:

Cable Matters USB C to HDMI Cable, Supporting 4K 60Hz (USB-C to HDMI Cable) in Black 6 ft - Thunderbolt 4 / USB4 Compatible with iPhone 15 Pro Max Plus, MacBook Pro, Dell XPS 13, Surface Pro and More

Cable Matters USB C to HDMI Cable, Supporting 4K 60Hz (USB-C to HDMI Cable) in Black 6 ft - Thunderbolt 4 / USB4 Compatible with iPhone 15 Pro Max Plus, MacBook Pro, Dell XPS 13, Surface Pro and More

smile.amazon.com

I can use either display, but only via the USB-C cable - I can no longer get any picture on either monitor via HDMI. I don't have room for another USB-C cable due to other thunderbolt devices.

Any ideas whats going on? I saw a few threads in the fall about similar issue, but they don't have any recent posts.

 

[djc6]

SMC reset fixed it.

Shut down mac
Hold down power button for 10 seconds

Seems fine now!

 

[tstimper]

https://forums.macrumors.com/threads/mac-mini-2018-hdmi-failes-after-os-upgrade-patch.2221573/

 

[ikaka]

SMC reset fixed it.

Shut down mac
Hold down power button for 10 seconds

Seems fine now!

Yup, I have to do that like 3-4times every time I reboot or cold boot, pisses me off. (and no I don't want an adapter, no room)

 

[tstimper]

today i found that removing power from the mac mini 2018 for some hours fixed HDMI.
But i expect that the issue will come back after the next update. You could test this. Make a backup, than internet recovery to Mojave -> HDMI ok -> than update to Catalina -> HDMI fail. Than the behavior would be confirmed at another Mac mini 2018. I have seen this with three different logigboards. This is #macmini2018hdmigate . Apple needs to fix this soon. Otherwise this device goes back to Apple ...

 

[bsbeamer]

Unplugging power for several hours is basically doing the same as PRAM/NVRAM reset in background:

Reset NVRAM on your Mac - Apple Support

If one or more settings stored in NVRAM don't work as expected on an Intel-based Mac, resetting NVRAM might help.

support.apple.com

 

[frou]

Unplugging power for several hours is basically doing the same as PRAM/NVRAM reset in background:

Reset NVRAM on your Mac - Apple Support

If one or more settings stored in NVRAM don't work as expected on an Intel-based Mac, resetting NVRAM might help.

support.apple.com

Isn't the whole point of the "NV" in NVRAM the exact opposite? i.e. that it doesn't require power to retain its contents.

 

[tstimper]

funny, a NVRAM (se https://de.wikipedia.org/wiki/NVRAM) wich is actually only a temporary NVRAM for some hours. But the point is that there could be a problem with NVRAM on Mac mini 2018 which corrupts stored settings and this breaks HDMI. #macmini2018hdmigate

 

[ikaka]

confirmed, removing power for few hours restores hdmi on the 1 boot, vs pram/nvram reset takes 3-4 times.

 

[tstimper]

ok, so NVRAM has corrupt data which breaks HDMI. Ckearing NVRAM fix this.
There are two questions:
1. which data get corrupt? Is there something we can do with a script to fix this?
2. is this normal behavior that NVWAM loose his data after some hours without power is is this a hardware error?

 

[bsbeamer]

Anyone with this issue have Windows/Boot Camp installed? Created major issues with corruption in MP5,1 and exacerbated with incorrect Windows install method. Most noticeable when trying to update firmware and unable. Required 3+ resets and even then occasionally would fail. Some needed manual cleanup by users. Beyond technical skill for many.