Unfortunately I’m in a “throw it out or fix it” situation with this. My TB Monitor situation started to happen more often, and on a few occasions became a crisis as I can’t do my work without a second monitor (film editor). I bought a new Dell 3219Q monitor to replace it, but since the TB monitor does indeed work 98% of the time, I would love to find a way to fix this issue so I can have a large dual monitor setup. I know that, at least in my case, along the way I’ve disproved all the theories in this thread, including my own.
Here are things I know:
• If power to the TB Monitor was turned off for a while (overnight, typically), the issue would almost always happen - the computer would ‘see’ the monitor, all functions and things hubbed through the monitor would work just fine, but the display was black.
• I changed ports, cables, adaptors and finally even the computer, using a brand new MacBook Pro, but the problem continued no matter what I did.
• It’s not a software or firmware issue, either with the monitor (it has that last firmware update) or computer (because it happened with a different, brand new computer, running Apple’s off-the shelf Catalina instead of Mojave on the older computer).
• Once, the monitor just went black during the day as I was working. Everything continued to work just fine, but the display was completely off.
• Pulling the power to the monitor for at least 20 mins or more was the ONLY thing that could bring it back to life, but doing this for hours did not guarantee it coming back. In every case that the display has gone black, it has eventually ALWAYS come back - at some point. But I’ve had to leave it alone for a day or two to get that. Suddenly, it would just work.
• I just went back to using the built-in cable ganglion and that works, and fails, just as much as a direct cable in into the back of the monitor did.
• I removed absolutely everything plugged into the back so there is no power draw other than monitor.
Given all the above, I didn’t bother installing the new laptop power/TB cable ganglion I bought here, as that’s clearly not the issue.
When working, it’s still a great display, and now that it’s just sitting on the shelf unused I’d love to crack it open and fix it if I can. Assuming the problem does not lie in the incoming cable ganglion or TB socket on the back of the monitor, and that it seems somehow connected to power issues, I’m going to try replacing the power supply, available here.