I purchased a Mac Mini 2018 and connected it to my Dell 42" monitor via HDMI. I works fine except that the screen goes black intermittently and comes back after 3 or 5 seconds. The monitor and cable works well with other computers. I also checked the connection and upgraded the OS to the latest one. Nothing helps.

I unplugged the HDMI cable and plugged it into USB-C using an adapter. It has no problem. So I guess the HDMI port has an issue.

Do any of you have this problem?

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  • can you look in the console to see what is it doing – Ruskes Nov 11 '18 at 23:53
  • what HDMI cable are you using ? 1.4 or 2.0 – Ruskes Nov 12 '18 at 0:00
  • I too have had the same problem with my new Mac mini, barely a week old, connected to a Dell monitor via HDMI. It's happened randomly, for a few seconds and reverts back to the active screen. I have installed the latest OS version too. I'll try plugging it in via a USB-C adaptor as suggested - the HDMI cable worked fine just days before.It's bit of a sinking feeling after shelving out a shed load of money. – Jules Nov 26 '18 at 21:38
  • Have you sent any bugreport to Apple? I have just bought a Mac Mini 2018 and I am affected too by this problem. The operating system is Mac OS Catalina – Germano Massullo Oct 18 '19 at 8:06

I don't have the exact same problem, but the HDMI port does seem to behave a little oddly; the signal doesn't appear to be 100% perfect - during boot, wakeup, or after display mode changes, some of my displays will briefly show a distorted image. Either the colours are off, the image is shifted, the image is briefly simply noise, etc. but it seems to settle down OK after a few seconds on the displays I have and so far has not recurred once the image has "settled in".

I do have one screen (Acer XR341CK, 3440x1440 75Hz) which is detected but shows no image at all when connected via HDMI 2.0 and native resolution is selected (lower refresh rate or resolution works). (It is not detected at all by the 2018 Mac Mini when connected via a USB-C to DisplayPort cable, suggesting the GPU in this Mac somehow doesn't like this display. Update: At some point during the 10.14.x OS update cycle, the display started working without any troubles when connected via a USB-C to DisplayPort adapter.) The same display works as expected on other Macs and indeed when connected to an eGPU on this Mac Mini.

I believe the reason for this is that the Mac Mini 2018 uses an active HDMI 2.0 converter chip to produce an HDMI 2.0 signal from the GPU's native DisplayPort 1.2 output signal. Without this, the GPU would only be able to output HDMI 1.4 natively, which maxes out at 2560x1600 @ 60Hz or 4K @ 30Hz. Intel's GPUs are woefully out of date in this regard. (HDMI 2.0 supports 4K @ 60Hz)

The USB-C to HDMI cable is a fine solution if the above mode restrictions are OK for your display; otherwise, if your display has a DisplayPort input, I recommend trying a USB-C to DisplayPort cable. Apart from that Acer display, this is working fine on all other displays I've tried too, including those that have shown the brief image corruption I mentioned via HDMI.

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  • I can attest to the weirdness of HDMI in my Mac mini 2018. Once I switched to a USB-C to DisplayPort cable for my monitor, all the weirdness is gone. – jamix Sep 29 at 9:13

Actually you may have run into something I have run into from time to time with Apple hardware: seemingly good hardware fails or fails intermittently on Apple hardware.

I have chalked it up variously to "Apple's high standards," "not completely compatible," "why, Apple, just why?!"

It is most likely just what you have found out, a completely good HDMI cable. And another "completely good HDMI cable" may have similar results, fail completely, or work perfectly.

Me, I'd buy another cable (different brand, with a good return policy) and give that one a try.

It could be a problem with the cable or the port on the Mac. But unless it's a really cheap HDMI cable that you can blame on crappy manufacturing in (insert country of choice here) it is merely an inexplicable incompatibility that you may never know the cause of.

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  • I have a MacMini 2018 on OSX 10.14.6 into a Sonnet Breakaway Box (Apple Dev Edition) with RX580 GPU, connecting to a ViewSonic VP2780 monitor. I am recently experiencing the black flickering issue via the HDMI->HDMI cable (even if I swap cables). So... I changed the eGPU/monitor connection with a DisplayPort->DisplayPort cable and we're good. – zzyzy Jan 29 at 3:48

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