27" imac and 23" Cinema Display not waking

[bodtwo]

Hi all,

I've a late 2011 27" imac with an aluminium 23" Cinema Display that's been running fine up until I installed 10.9.5. Since then the external display is not coming back on after the screens have gone to sleep.

The only way I can get it to work is to pull the power cable from the Cinema Display, plug it back in and when I do that the imac recognises it and it works.

I've tried a PRAM and SMC reset but the problem persists, I've even installed Yosemite but I get the same issue.

Any ideas?

Thanks all.

 

[bodtwo]

No guesses?

 

[eduardrw]

Won't help you debugging your problem but:
I run a 27' late 2009 iMac with 30" Cinema display - no problems with wake ups at all.
Maybe time for a clean install.