Random Black Screen - Backlight Shut Off - Solved!
Answering my own question here simply to provide a solution that I have not seen listed anywhere else before!
Imac 27" 2009 & 24” Cinema Display - Random Black Screen - Solution
iMac 2009 27", computer works fine however at random points the screen will go black. Checking the screen with a torch I can see the LCD is still on and working as it shows my desktop.
I have hot corners with display sleep turned on so if I move the mouse to the corner the display (while already black) properly sleeps, moving the mouse a second later causes the screen to come back on again fully lit.
The time between black screens can be totally random. Sometimes it works for weeks with no problem. Sometimes the black screens return within minutes or even seconds. This happens with the screen being used both directly and in Target Display Mode.
- Reset PRAM / NVRAM
- Reinstall OS - same problem on Sierra, High Sierra and Mojave
- Running the fans at higher speeds
- Open the iMac and clear out any dust
- Reseat all internal cables
None of these fixed the issue. Sometimes they would appear to resolve it but the problem always came back.
Updated as for some reason this gets rejected when trying to add a comment:
Here are the parts to fix the problem…
Cinema Display replacement part was "LED Backlight Lamp strip 60leds for 24" Cinema Display A1267 MB382LL"
2009 iMac was replacement part "310mm LED Backlight Lamp strip bar 36leds For Apple 27" LCD LM270WQ1 SD C2 M270WQ1 SDA2 SDB1 SDE3 SDE5 SDF1 LGT2781 LGT22795"