Bruce Thomson1

Q: Flashing Repeating pattern on 20" Cinema Display

Some time ago, my 20" Cinema Display model # A1081 (new 10/2007) went dark. Today I tried to use it again and of course it still does not work, but I did notice a repeating pattern flasing in the white LED in the lower right hand corner: In Morse code, it would be dot dash dot repeating eveyr 7 seconds or so. This must mean something specific and I would like to know if I should consider a new power supply or is it a diffrent problem.

MacBook Pro 2.4GHz, Mac OS X (10.6.5)

Posted on Apr 3, 2014 2:00 PM

Close

Q: Flashing Repeating pattern on 20" Cinema Display

  • All replies
  • Helpful answers

  • by Bruce Thomson1,

    Bruce Thomson1 Bruce Thomson1 Apr 3, 2014 2:42 PM in response to Bruce Thomson1
    Level 1 (0 points)
    Apr 3, 2014 2:42 PM in response to Bruce Thomson1

    A little searching and I found the description of the problem in an Apple document (link below). The repeating short-long-short pattern action reads:

     

    Make sure you are using the correct power adapter with the display. This alert will only appear on displays built in 2004 or later which require an external power adapter.

     

    Other information implies that this is insufficient power from either a power supply failure OR excessive current draw by the back lights with age (in which case the power supply is now effectively inadequate) OR a spurious detection of that condition by the monitor. Seven years old, I'm thinking it's not worth any effort.

     

    http://support.apple.com/kb/ht2811

     

    There is a YouTube video about a "repair" that insulates the center pin on the power supply to Cinema Display to fool the display into thinking everything is OK. One comment on that video:

     

    To the people using this tape method to fix your Cinema Display. Keep in mind that the problem is caused by a failing 3.3v regulator on the logic board inside the screen case. Taping it will force the screen to keep working, and given time, will probably kill the logic board. The proper repair is to remove the logic board, and replace the 3.3 volt regulator. This regulator is connected to the PSU sense signal pins, so when it fails, it causes the display to think you have a defective power brick connected.