iMac 24" with external 24" Cinema Display - brightness control not working after upgraded to macOS Monterey

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iMac 24" with external 24" Cinema Display - brightness control not working after upgraded to macOS Monterey

I have my iMac 24" with external 24" Cinema Display running perfectly in macOS Big Sur, but the brightness control became not working after upgraded to macOS Monterey. I have tried unplugged/re-plugged the USB, display adapter, power point, restarted iMac, but the brightness control is only able to control the iMac main display, not the external Cinema Display. Could this be a bug in USB display extension in Monterey?

iMac 24″, macOS 12.0

Posted on Oct 27, 2021 4:16 PM

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Answer 1

Top-ranking reply

leoluzacmp

Level 1

41 points

Oct 29, 2021 4:52 PM in response to cheesiong.yee

I have a similar problem connecting a Mac mini to a 27" Led Cinema Display. I solved the problem for now, using the MonitorControl app. Details in: https://forums.macrumors.com/threads/no-24-cinema-display-brightness-control-monterey.2319531/

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Answer 2

Eric--F

Community Specialist

Oct 28, 2021 2:27 PM in response to cheesiong.yee

Hello cheesiong.yee,

Thanks for asking the Apple Support Communities about your new iMac and the cinema display brightness controls. We're happy to check this out with you.

Please start with this help article. Make sure everything is hooked up properly and the controls in System Preferences are showing correctly per the article: Connect an external display to your iMac - Apple Support

"Adjust and arrange displays. After you connect an external display or projector, use Displays preferences in System Preferences to set how the displays are arranged, turn screen mirroring on or off, and make other adjustments to color, resolution, and more."

If this is not working as the article shows it should, test if the same thing occurs in safe mode: How to use safe mode on your Mac - Apple Support

If it still is not working as described in the article above, check if the same thing occurs in a newly created unmodified test user. This isolates the issue from your account to system wide: Set up users, guests, and groups on Mac - Apple Support

Let us know the results of the testing and if it works properly in System Preferences. Thanks.

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Answer 3

Oct 28, 2021 4:08 PM in response to Eric--F

Have tried the following just now and test the brightness control for the external Cinema Display,

Reconnect both USB-C to mini DV adapter, USB connection, power connection of the Cinema Display -> not ok
Changed different Thunderbolt port, different USB port from USB Hub -> not ok
Boot to Safe Mode -> not ok
Use Guest user -> not ok
Created new user and login to it -> not ok

The brightness control only able to control the iMac main display but not the external Cinema Display. It was working fine before upgraded to macOS Monterey. BTW, the display on the Cinema Display is ok, but not able to control the brightness. I also confirmed the USB in Cinema Display is working as I connected my UPS USB to the Cinema Display and the UPS Power reported correct. Thanks.

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Answer 4

Oct 29, 2021 3:26 PM in response to Eric--F

Thanks. I have created a Apple Support case, chat with 2 advisors, phone call with 1 supervisor, but still cannot resolve the issue, and finally the supervisor said could be due to the Monterey update has updated the firmware that no longer support such a old Apple Cinema Display.

After some more self checking, I doubt the firmware update is the issue as the display, audio, camera in Apple Cinema Display is still working fine, only the brightness control is not working. And my USB hub (connected to iMac USB-C port) is working fine (as screen below).

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Answer 5

Eric--F

Community Specialist

Oct 29, 2021 12:09 PM in response to cheesiong.yee

Hello cheesiong.yee,

Thanks for trying the troubleshooting and the detailed reply. Since it is not working in safe mode or a test user, it seems this is system wide and not caused by third-party products.

Please contact Apple Support for more help with this: Contact - Official Apple Support

Thanks.

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Answer 6

Oct 29, 2021 5:15 PM in response to leoluzacmp

Thanks @leoluzacmp. The MonitorControl app with DCC Max 250 works perfectly for me. Thanks again. From the macrumors forum, looks like this is a bug in Monterey.

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Answer 7

SewCM

Level 1

8 points

Nov 6, 2021 5:40 AM in response to cheesiong.yee

I called apple and they said the same thing. Apple Cinema Display is a Classic Product and doesn't have support to Monterey. I hope they'll solve this issue.

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Answer 8

Nov 6, 2021 10:35 AM in response to SewCM

I think it could be Apple management/support decision, not technical limitation, as the MonitorControl app is working fine.

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Answer 9

Dec 12, 2021 5:08 AM in response to cheesiong.yee

This fixes it completely! https://lunar.fyi/

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iMac 24" with external 24" Cinema Display - brightness control not working after upgraded to macOS Monterey

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