Replying to Matt00 and Rocky:
I'm new to forums and hope I'm doing it correctly.
I have been having the same exact symptoms as Rocky and if my more mature memory serves me well, Apple Care senior advisors already did a number of reset like things with me including ACL plus different preferences changes, though I forgot which ones....
I am wondering a few things for Matt00 setup:
(1) What year is your 30" ? And do you have 4 cords coming from it?
(2) how do you have your 30" connected?
(3) What additional connectors including adapters are you using?
Last week I was in an Apple store re: my 30" intermittent illumination and a Genius told me that there is no 100% stable effective way to connect the 400 Fwire male from my 2006 30" into the 800 Fwire female port of my mid-2012 Mini BECAUSE the adapter I have between them is for DATA transmissions NOT display transmissions (my non-tech wording). She said that this would account for the monitor illuminating sometimes and sometimes not.
Wanting to know anyone's response to what I just wrote. How does this sound to you? Anyone try any creative ideas, or workarounds?
Good Luck and Blessings for each of us working with this.