[From Tuesday, May 27th]
Description of the problem First, a quick recap of what dozens of iMac flat-panel owners are reporting to MacFixIt.
The problem appears to affect both 15" and 17" flat-panel iMacs, and is occurring for some users as soon as a few weeks after purchase. Essentially, the system never wakes itself from the dimmed level that accompanies sleep - so when you re-awaken your iMac, the screen content is barely visible. The only cure, in most cases, is a hard restart; or by using a desk lamp or some other outside light source to navigate through the dimmed screen for a soft restart.
Setting too low in some cases In some instances of this problem, the display's brightness level is inexplicably lowered when waking from sleep, and simply needs to be raised using the keyboard controls, or by navigating (again by some external light source) to the Displays pane in System Preferences.
Some users have even been able to revive their systems' displays by continually generating mouse and keyboard activity. Leo O'Campo writes:
"I have seen this dimming anomaly in the lab at school. We have 20 iMac 15" flat screens and they all do the same thing, but only if they were sleeping more than 5 minutes. If you hit the space bar and move the mouse several times they come back to life fully. Seems to me that these iMac flat panels work much like my teenager in the morning."
Another possible workaround is to enter the Energy Saver pane of System Preferences, set computer to "Never Sleep," and use "separate time to put the display to sleep." Optionally, check the box "put hard drive to sleep whenever possible."
In other instances, hardware needs to be replaced.
What needs to be replaced Users experiencing the dimming problem - and unable to resolve it by raising the brightness level - should immediately invoke their Apple warranty, or AppleCare coverage. Readers have had success getting the proper hardware replacements through these venues, as well as retail Apple locations if their machines were purchased there. One reader writes:
"I took it right back to the Apple Store where I bought it, and they mentioned the inverter board, as if they had seen this before. I believe they replaced the display unit, though they used my existing display 'case' and bezel. Thankfully, the display was not crooked when I got it back, nor did it have any dead pixels. It's been running fine for the past 2 months. I have it set to never sleep, with separate display sleep timing - I have to keep iTunes streaming available when I'm at work, but I certainly don't want my display lamp to "burn out" sooner by leaving it on all the time."
Meanwhile, an anonymous Apple Certified Desktop Technician lets us know that several machines have come into his shop with this problem, and replacing the machine's logic board was the required fix.