HDMI out from Mac Mini seeing scan lines and flicking
[Re-Titled by Moderator]
What make and model is the display...?
If you have a long cheap VCR to TV HDMI cable...?
Get and test a short 3.3ft high speed certified HDMI cable.
for example: https://www.amazon.com/8K-HDMI-Cable-Highwings-Braided/dp/B08NX5CZTF?
It looks like matching the refresh rate to 60hz did the trick. Day and a half and no issues. I'll still likely replace the Dell monitor with one that can do a higher refresh rate. Thanks again for your help
Ah OK, your running dual displays and one is thru a Hub.
What Hub..?
Hub's can cause Resolution, Refresh Rate and connection problems.
First thing that I would do, is by-pass the Hub and connect both displays directly to the M4 Mac mini.
Also note: that the M4 Mac mini can support 2 displays connected directly to the Thunderbolt/USB-C ports.
see video support at > Mac mini (2024) - Tech Specs - Apple Support
and > Connect a display to Mac mini - Apple Support
If by-passing the Hub doesn't help..?
I would test both displays on short high speed USB-C to DisplayPort 8K cables.
for one example: https://www.amazon.com/dp/B08B3SB5VC/ref=sspa_dk_detail_2?
FWIW you might actually get by with just one new short high speed USB-C to DisplayPort 8K cable.
Put the Dell on your existing USB-C to DisplayPort cable and use the upgraded 8K cable for the M27Q.
Dell S2721QS. Max rez is 60hz. Other monitor (off USB-4 hub/ Display Port) is a Gigabyte M27Q Rez at 170hz. Disconnecting the other monitor/hub makes no difference and several different hdmi cables have been used along with different hdmi inputs on the monitor.
Next thing I'll try if/when it happens again is to set the M27Q to 60hz also. Hate to do that because it doesn't look great when I do
Using the TB ports (1 for the Hub/ 1 for an OWC TB 4 hub/ 1 for a Rodecaster Duo audio interface which can't go through a hub). The Mac mini M4 Pro does have the two front ports that are UBC-C that I could connect the Duo to.
I have a USB-C cable to HDMI that I will try next. The M27Q is connected through the hub and is working fine. I had the Dell connected to the Mac mini HDMI port. That's the one causing problems.
Last thing I did was drop the Rez on the M27Q to 60hz to match the Dell. Waiting to see if it happens again.
BTW thanks for the help[ and quick responses. Greatly appreciated
Yea' you'll have to experiment with different cables and connections to see what works best.
You're welcome.
Good work, thanks for the update. You're welcome.
How can I fix scan lines on Mac mini M4 display
