Weird interaction between TV and Apple LED Cinema Display

CatalogK9 · 04-15-2025, 03:55 AM

I've posted recently about this my old Apple LED Cinema Display (mini-DP to DP) being seemingly stuck at 0% brightness, so TL;DR: it seems to be working except the screen is black and nothing seems to be able to turn the backlight back on via hardware controls like it used to.

Here's the plot twist:

I plugged my TV into the dock via HDMI, and it works, BUT only when DisplayLink Manager is running, AND it doesn't show up in the menubar drop-down, AND if I turn off the LED Cinema Display in the drop-down menu, my laptop can no longer detect the TV (though the picture stays on, not sure what that's about).

Even though I set the TV to work as an extended monitor separately from the LED Cinema Display, the screen recording menubar thing only shows what I'm sharing to the LED Cinema Display, not the TV, which seems to be working only as long as the LED Cinema Display is connected and activated in the manager.

My laptop still isn't able to control brightness for anything but itself. The MonitorControl app USED to work for my LED Cinema Display but stopped working for it at the same time the problems started. I tried Better Display after the problem started, to no avail, but did see something in the advanced settings that worries me as to the potential root cause of my problems with my old Apply display:

There is an option (which I have NOT activated) to "Treat as generic third-party (non-Apple) display", with the description "Treat this display (identified as Apple-made) as generic and allow DDC control to be enabled. Might cause permanent issues on some older Apple displays!"

I did not try using either app during my TV test, as I didn't see how the TV being connected would suddenly bring back hardware brightness controls for my Apple display, but almost as soon as I started typing up this update to hopefully help narrow down the problem, this warning about DDC controls causing permanent issues with older Apple displays popped into my mind, and now I'm worried my display might actually be borked from the latest DisplayLink Manager update.

The weirdest details remain to muddy the waters: my display went dark BEFORE installing the latest DisplayLink driver, and NOT immediately after any MacOS update (I was on 15.3 already for some time without any issues), and starting up in Safe Mode during troubleshooting has more than once brought my screen back for life for an instant, exactly as it should look, so it's not completely broken in any case.

I'm not sure how any of this information will help, but data is data, and anything I can do to potentially get my setup (and desk space) back to normal is better than nothing, so I hope the team finds a lead in this mess somehow.

04-15-2025, 03:55 AM	#1
CatalogK9 Junior Member Join Date: Mar 2022 Posts: 11	Weird interaction between TV and Apple LED Cinema Display I've posted recently about this my old Apple LED Cinema Display (mini-DP to DP) being seemingly stuck at 0% brightness, so TL;DR: it seems to be working except the screen is black and nothing seems to be able to turn the backlight back on via hardware controls like it used to. Here's the plot twist: I plugged my TV into the dock via HDMI, and it works, BUT only when DisplayLink Manager is running, AND it doesn't show up in the menubar drop-down, AND if I turn off the LED Cinema Display in the drop-down menu, my laptop can no longer detect the TV (though the picture stays on, not sure what that's about). Even though I set the TV to work as an extended monitor separately from the LED Cinema Display, the screen recording menubar thing only shows what I'm sharing to the LED Cinema Display, not the TV, which seems to be working only as long as the LED Cinema Display is connected and activated in the manager. My laptop still isn't able to control brightness for anything but itself. The MonitorControl app USED to work for my LED Cinema Display but stopped working for it at the same time the problems started. I tried Better Display after the problem started, to no avail, but did see something in the advanced settings that worries me as to the potential root cause of my problems with my old Apply display: There is an option (which I have NOT activated) to "Treat as generic third-party (non-Apple) display", with the description "Treat this display (identified as Apple-made) as generic and allow DDC control to be enabled. Might cause permanent issues on some older Apple displays!" I did not try using either app during my TV test, as I didn't see how the TV being connected would suddenly bring back hardware brightness controls for my Apple display, but almost as soon as I started typing up this update to hopefully help narrow down the problem, this warning about DDC controls causing permanent issues with older Apple displays popped into my mind, and now I'm worried my display might actually be borked from the latest DisplayLink Manager update. The weirdest details remain to muddy the waters: my display went dark BEFORE installing the latest DisplayLink driver, and NOT immediately after any MacOS update (I was on 15.3 already for some time without any issues), and starting up in Safe Mode during troubleshooting has more than once brought my screen back for life for an instant, exactly as it should look, so it's not completely broken in any case. I'm not sure how any of this information will help, but data is data, and anything I can do to potentially get my setup (and desk space) back to normal is better than nothing, so I hope the team finds a lead in this mess somehow.