Display flickers briefly then goes black after connecting mini dp

Can you shine a flashlight at the display at an angle, do you see a faint image of your desktop? If you do then the backlight WLED driver is likely blown.

"I have the exact same error, but it's intermittent and the problem mostly arises after power has been entirely disconnected from the display, i e disconnecting the power cable or switching an outlet off. As long as the computer just sleeps the display, it will often start up again.

When I get the flicker problem, sometimes one of two things helps to get it running again:

Connect it to a laptop and adjust the brightness setting of the Cinema Display. Results may not be instant, and doesn't always work but often does. You can try to lower it, then crank it up to max. (Note: the USB cable needs to be connected for the brightness setting to appear)Like @janoslinde has done, connect it to an outlet with a powerswitch and try to power cycle it there. Often works for me. Connected to a Mac mini that can be forced turned off, the display sometimes comes alive when cold starting the Mini again (this seems to give the display a different type of signal than when the computer sleeps and then wakes up)

At this point, I'm considering

Changing the logic board (around 120-200 EUR on eBay)Getting a new Backlight WLED driver like @danj suggestedChanging the power supply (although multimeter reading shows it gives 24V, 12V, 5V, 3.3V just like it should). However it may be unstable, maybe some of the condensators bad? Costs around 100 EUR on eBay. Possibly buying a new Function and/or Backlight cable (internal cables) although it seems unlikely it would be damaged and suddenly (and temporarily) go bad as to shut off the backlight."

The power supply board may also be going bad. Does it work if you unplug power for a few minutes and then plug it back in? Usually it will work for 2-5 minutes and then the display will go black again.

"Sounds like the same problem I had. See:

What components need replacing on the Logic board?"

"Hi,

Same problem.

I tested your different options (replugging many times the power screen after 2s or 10mn) without any success.

But I was interested by the idea of “sending a different signal to the screen” to get the light back.

So I plugged the screen normally to my MacBook and I reset my NVRAM / PRAM (Turn on your Mac / press and hold the Cmd+Option+P+R keys immediately after your heat the startup sound. Hold these keys until the Mac restarts and you hear the sound again)

And during the reboot, the Led Cinema Display turn on normally"