24" display; Built-in iSight Camera, Microphone, and Speakers; 1920x1200 resolution. Released October 2008, identified by model number A1267.

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Why is my LED cinema display switching on and off?

Hi there

I've a problem with my 24" LED cinema display. The display is constantly switching on and off. I've used the Apple Technician Guide to check out whats wrong. I was going step by step trough it. What i found out is:

The volltage between TP11 and GND is not stable. It moves constantly between 22.7 - 23.2 VDC.

Also the connector cable voltage (Pin 1 and GND) from the power supplay is moving constantly between 14.3 - 14.8 VDC.

All other voltages are stable and in the needed range. It looks like the power supply is somehow not working correct.

On the power supply unit its is no damaged part or short visible.

So before ordering a new power supply for 250$ from US to Switzerland my questions:

- Can somenone confirm that most likely the power supply has to be replaced?

- Is it possible to check and maybe repair the power supply itself?

Thank you very much in advance for any help!



Answered! View the answer I have this problem too

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You don't provide any background or history... see if this thread from Apple is any help.

If this Answer is helpful please remember to return and mark it Accepted.

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I've used the display on a Mac Mini (2010). Also testd it on a MacBook (2010). Same problem. If i connect the Mini Display Port to the Mac Mini, the Display stays black but "tries" to show a picture. Every 2sec it shows a picture for 0.5 sec, like a "flash". So for a verry short time the display works and then turns black and so on. Mag Safe, USB and Speakers are all working fine. Seems not to be a software issue.


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I currently have a similar issue with my 27" display. Many times it will not come on at all, but all USB devices, speakers and the charge cable from the display function. When I play around with unplugging it and switching between outlets I sometimes get it to come on and work again, or just get the second flash before it goes dark.

I've read on the Apple support site that the Genius bar will sometimes replace the power supply or the logic board, but they're replacing both in a lot of cases.

Ifi decide to do the repair myself. I'll post my findings here.

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Apple 30" Aluminum Cinema Display A1083 Control PCB Board LM300W01 6870C-0129E

Replace your PCB Board with a used functioning board. It will solve your problem.

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Marcel will be eternally grateful.
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