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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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Sam

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  • can you look in the console to see what is it doing
    – Ruskes
    Nov 11, 2018 at 23:53
  • what HDMI cable are you using ? 1.4 or 2.0
    – Ruskes
    Nov 12, 2018 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, 2018 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 Oct 18, 2019 at 8:06
  • I have this problem with a mac mini M1; that I just bought. The screen blanked out for a bit while typing this.
    – Rob
    Mar 29, 2021 at 5:44

2 Answers 2

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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, 2020 at 9:13
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    I see this intermittent black screen even when using a USB-C to DisplayPort cable. Today, I've seen the black screen 15 times! I'm trying an HDMI to HDMI cable to see if this works. Jan 7, 2021 at 19:21
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    @PaulLefebvre I've found that a high-resolution display connected via DisplayPort to the USB-C connector is quite sensitive to electrical interference, which causes intermittent black screens. Things like plugging in USB3 devices to another computer nearby or even just moving the cable will trigger it. Now, my desk is rather full and probably really bad for EM interference, but my suggestion would be trying shorter and better shielded cables if at all possible.
    – pmdj
    Jan 7, 2021 at 19:47
  • Thanks for the tip. So far, the HDMI to HDMI cable has had no black screens, so perhaps I do just need a higher quality and better shielded USC-C to DisplayPort cable. Jan 8, 2021 at 20:03
  • @PaulLefebvre if HDMI will do it, then that’s probably preferable anyway as the Thunderbolt ports are useful for so many other things than displays too. Unless of course you want to use the HDMI port for another display.
    – pmdj
    Jan 8, 2021 at 21:17
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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, 2020 at 3:48

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