Chosen Solution
#1- Apple A1407 Display Does Not Always Display At Startup Unless Via F12 Voiceover commands for Username/Pword. Othertimes, perfect startup in a blink of the eye. Thunderbolt Display connected to Mac mini 2018 MacOs 10.15.6 via Thunderbolt adapter to USB-C. I’m skeptical of the display because no issues to TV but that’s HDMI signal not Thunderbolt. I’ve repaired the A1267 and hoping not to mess with this one. #2-How hot is too hot for this display? Fan is running. #3-Should Display USB ports always have constant power when Mac is off? Will not charge phone constanlty Thanks in advance.. Update (07/02/2020) What’s supposed to be connected here? No extra parts found
What I find interesting is the Fn 12 is the volume up key, so why would this alter the display? Thats just so odd! The display does have a speaker! So the signal is being passed via TB to the audio processor within the display to increase the volume. But why would that make a difference? Apple Thunderbolt Display Teardown Review Step 11 You also talked about loosing power on the USB ports. The ports are powered by the displays power supply and should stay on with or without your system running. So thats point to the power supply as suspect! I would open the unit and check the voltages to see if I could narrow down if the power supply or the logic board needs attention. Update (07/02/2020) The fan unit has a thermal sensor within it. If you look at the fan you’ll see you have the fan power and tach connection and the second is the thermal sensor
Replacement AIO cable listed as NEW, has a defective Thunderbolt Cable. Connecting the A1407 Display directly to the 2018 Mac Mini with a dedicated ThunderBolt cable (plus adapter) yielded a perfectly operating display with Display Brightness control, speakers, mic, camera, etc. Seller is sending another AIO and the elusive missing LCD Thermal Sensor that was stumping the pros. Logic Board ok at this time. Case closed. Thanks!
