4 Replies Latest reply: May 3, 2014 6:48 PM by Erik Sawaya
Joseph Coates Level 1 Level 1

This is not so much a question as an observation.


I was using a 1920 x 1200 Cinema HD Display 23 inch (LCD) with my iMac as a second monitor. I needed to move it temporarily to a Mini. I unplugged it hot from the iMac and hooked it up to the Mini.

Black. Nothing.

System Profiler and Displays in System Prefs showed it as active and working. But the little blue LED on the front was off and the screen was dead.

After making sure it was not lint, unplugging and plugging back in, restarting, etc. I tool the display back over to the iMac.

Same with it. Less than 30 minutes earlier, it had worked for weeks fine on the iMac.

I did searches here and on the web to see it this was a common problem. I did see things about bad power supplies and similar (although not exact) HD displays. I also kept seeing expensive repairs.

Because I was pooped from working in the yard over the weekend. I decided to unplug it, shut off the iMac, and try in the morning.

The next morning, no problems at all. Whatever it was, seemed to reset. The display is working fine again on the iMac.

So if you have a Cinema HD Display go black on you but still shows up in System Profiler and Displays in System Prefs as on, don't panic. Go have lunch. Go home. It might just come back on after being unplugged for some time.


I guess this is the question: What happened?


BTW: it had previously been used for years on the Mini before being needed on the iMac. I hooked another non Apple monitor up to the Mini and it worked fine. So, it was not a Mini issue and, also, it failed to come on when brought back to the iMac, at first.


Something reset in the Cinema HD Display when left unplugged.

Apple Cinema Display (23-inch DVI), Mac OS X (10.6.8)
  • X423424X Level 6 Level 6

    If I understand waht you are saying is you hot swapped the display from one machine to the other.  In other words both machnes were already up when you unplugged one and plugged into the other.


    Normally you should be able to do that although you may need to fiddle with the Displays preferences a bit (Detect Display for example).  But apparently that wasn't working for this display.


    Booting up with the display already connected should certainly work.  And if I understand you it did.


    Sometimes smc and pram reset should be done when changing hardware configurations as well.

  • Joseph Coates Level 1 Level 1

    The Mac Mini was off when I hooked up the display, not on.


    I turned off the iMac when re-plugging the display back in.


    I did fiddle with display prefs as first thing. No impact because the prefs *showed* that the Cinema HD was there and working! (Just black screen and no LED on front).


    Booting up on either machine did not work *until* some time passed (overnight in my case) with the Cinema HD disconnected and unplugged.


    In decades of using the Mac, I have never seen a pram reset solve anything but does mess up alot of things 99.9% of users would rather leave alone and unmolested. Techies love PRAM reset as a first go to because it is a lazy quick fix. But, it actually never fixes most problems. It is overkill 99.9% of the time.


    SMC reset for Intel Macs is just unplugging the computer for 15 seconds. Again, have never seen this fix any Mac problem in decades.

  • X423424X Level 6 Level 6

    I won't debate with you except to point out the number of times smc reset has helped users in these forums and to a lesser extent pram reset.  And maybe it was your experience in older machines but these do not really change much of anything significant to the user but may clear some ills up.  They are particularly useful for many bluetooth problems.


    Speaking for myself I use them whenever I make a configuration change (add/remove ram, connect/disconnect a monitor, add/remove an internal drive) in my mac pro.  I know it works in those cases because almost every time I change configurations I cannot sleep my machine.  Attempting to do so causes the fans to rev up and the machine to immediately wake up.  And 100% of the time that this occurs the smc/pram resets fix the problem. 


    Fortunately changing confiurations does not happen that often for me.  But when it does smc/pram reset is an easy fix.  And nothing else suffers as a result of it. 

  • Erik Sawaya Level 1 Level 1

    Did you ever fix it? I have the same except my led on the front is still on, screen is black.