IMac Target Display Mode black screen

target-display

I use an iMac with Target Display Mode from a Macbook Pro. Sometimes when I enable Target Display Mode, the iMac screen stays black, even if my Macbook Pro's display suggests that another monitor has been plugged in (apps move away from the screen).

How can I fix this?

Best Answer

On the Macbook, change the rotation on the iMac display to 90°, then revert it back (or let it revert back after the timeout) to Standard. That seems to snap it out of its zero-brightness funk ~~more or less every time~~ much more frequently than other display changes.[1]

(Of course, you can't do this in clamshell mode, you need some functioning display to use System Preferences→Displays on.)

[1]: (I've seen it fail once or twice, but it is the most reliable workaround I've found yet.)

Related Solutions

IMac – How to share keyboard and mouse in Target Display Mode

I solved this issue using a Griffin PowerMate (basically, a USB-wired button) and some AppleScript to switch Bluetooth off on the iMac, freeing up the keyboard and mouse so my MacBook (connected via TDM) could take over.

It's very smooth (as smooth as can be for something non-standard). I just connect my MacBook to the iMac, hit cmd+F2 on the keyboard, then tap the button to disable Bluetooth and let the MacBook take charge. When I'm finished, I just unhook TDM, close the MacBook and tap the button again to reconnect the keyboard and mouse to the iMac's Bluetooth.

Details here - hope it's useful to someone else: http://jamesholland.com/post/80600076762/hacking-mac-os-x-to-toggle-bluetooth-for-better-target

Switch to Target Display Mode without keyboard

I found a way to do it with an old, white apple keyboard, haven't tested with others but it might work.

I used a tool called Karabiner from https://pqrs.org/osx/karabiner/. When you install it, enable following options to get Command + F2 to work:

F1..F12 to Functional Keys (Brightness Adjust, Music Control, etc)
- F1,F2 to Brightness Adjust
--- F1 to Brightness Down
--- F2 to Brightness Up

After enabling this option, hit Command + F2 having previously connected your macbook using thunderbolt cable. If you're lucky you'll have a new external display working!

Best Answer

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IMac – How to share keyboard and mouse in Target Display Mode

Switch to Target Display Mode without keyboard

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