User profile for user: Rakeshraju
Rakeshraju Author
User level: Level 1
4 points

How to fix a black screen on Mac mini (2014) after changing external display refresh rate?

Hello,


I post this to help other facing the same issue I had.


I accidentally changed the refresh rate of my attached external display of my Mac mini 2014 from 60Hz to 24Hz. Right after that, I got a black screen and a popup came up on my older Dell screen saying that I'm using the wrong refresh rate and have to switch back to 60Hz. I wasn't able to do that.


I tried different solutions after google-ing to reset NVRAM with cmd+option+P+R or boot into safe mode with shift key but every action leads again to the black screen.


also attaching a second monitor didnt helped me


so the only solution i had was to format my drive and install macos again through recovery mode only this step worked for me


To reset your Mac mini (2014) to factory settings, follow these steps:


Step 1: Back Up Your Data (Optional, but Recommended)


If you want to keep your files, back up your Mac mini using Time Machine or an external drive.


Step 2: Restart in macOS Recovery Mode


1. Shut down your Mac mini.

2. Turn it back on and immediately hold Command (⌘) + R until the Apple logo or spinning globe appears.

3. This will open macOS Utilities.


Step 3: Erase the Hard Drive


1. Select Disk Utility and click Continue.

2. In the left sidebar, select Macintosh HD (or your startup disk).

3. Click Erase, then choose:

• Format: APFS (for macOS High Sierra or later) or Mac OS Extended (Journaled) (for older macOS versions).

• Scheme: GUID Partition Map.

4. Click Erase, then close Disk Utility when done.


Step 4: Reinstall macOS


1. Back in macOS Utilities, select Reinstall macOS and click Continue.

2. Follow the on-screen instructions to install macOS.





Hope this solves your problem as it solved mine



[Re-Titled by Moderator]

Mac mini, macOS 12.7

Posted on Mar 21, 2025 10:56 AM

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User profile for user: MartinR
MartinR
User level: Level 7
22,537 points

Mar 21, 2025 12:23 PM in response to Rakeshraju

There is another way to fix this problem that avoids having to completely wipe & reinstall the Mac. But you need a second Mac to do this.


Assuming the first monitor was/is connected via HDMI,

  • Change to using a DVI adapter + DVI-to-HDMI cable. Depending on the exact Mac mini you have, you may need the Apple minidisplayport to DVI adapter (use with the 2014 Mac mini) or a USB-C to DVI adapter like this one (use with the 2018 Mac mini).
  • Connect the DVI adapter + DVI-to-HDMI cable to your monitor's HDMI input.
  • Boot the Mac mini. It will work because this is a different video out and your Mac mini will recognize the monitor and use the correct refresh rate ... but only for the DVI-HDMI connection. You need to change the refresh rate for the HDMI-HDMI connection but you cannot make that change while using the DVI-HDMI connection. Move on to the next step.
  • Open System Preferences (aka System Settings) and enable Screen Sharing. Exit, then shut down the Mac mini.
  • Reconnect the original HDMI-HDMI cable from the Mac mini to the monitor. Reboot the Mac mini. The screen will still be black. This is to be expected.
  • Using a second Mac, open a Screen Sharing window to the Mac mini. Go into System Preferences on the Mac mini (aka System Settings) and change the refresh rate back to 60Hz. Voila, everything works again!
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User profile for user: den.thed
den.thed
User level: Level 10
84,814 points

Mar 21, 2025 12:12 PM in response to Rakeshraju

Wow' reinstalling and then restoring or migrating from Time Machine is a rough ride, just to reset the refresh rate.

It is strange that the NVRAM reset, Safe Mode, disconnecting/reconnecting display does not default the refresh rate.


MartianR ran into this issues a couple of weeks ago.

see > Is it possible to reset the HDMI refresh … - Apple Community


If you have another Mac that is setup to access the Mac mini with Screen Sharing..?

You can use Screen Sharing to get into the Mac mini and change the refresh rate.


Another option is a Remote Desktop Management App from another computer or device.


If you do have Screen Sharing or Remote Desktop Management App setup..?

Connect a second Display or TV to the Mac mini and set up either one of those.

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How to fix a black screen on Mac mini (2014) after changing external display refresh rate?

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