imac A1312 2009 27inch, core2duo backlight goes away

[ielectron]

serial number W894716C5PM


I did not open this imac yet, the issue is the backlight, randomly goes away, then i press the power button to put into sleep, then press it again to wake it and the backlight comes back. When its off, like after 10-60 minutes, with a flashlight i can see the picture and mouse moving.
The backlight always comes back with this sleep-wake method, or by unplugging the power cable and start it again. Same if i boot from ext. hdd.

Fixed only few imacs before, what is the more likely to be faulty? screen? board backlight IC?

I dont have another imac screen to test with.

 

[dukefawks]

Bad soldering on the LED strips in the LCD. Need to totally pull apart the LCD, take out the 2 LED strips and reflow each LED and the connectors.

 

[Gurmon]

Just to add, this is a real mission separating the display first time. can be done, but high chance it goes wrong first time.

 

[Alan.L]

is this an common fault on all older iMacs and Apple Cinema Display (non-thunderbolt), like the one i just repaired?
i want to fix another one lol to improve my expertise..

 

[ielectron]

i took out the screen, and just looked around how can i reach the backlight, well it seem that i have to remove the whole metal back plate, that seems a huge job, and it not even sure the issue is there, maybe its a better idea to get another second hand screen to test with.

 

[Alan.L]

its actually very simple, remove the tape and any screws out of the way. then use a Metal Spudger to pry the frame out.
the screen cost too much.

 

[dukefawks]

I'm sure there are a few videos on youtube as these LCDs also have the common clouding issues by dust getting in the backlight diffuser. It is 100% the LCD and very very common on all 27" LCDs.
The easy way out here is to get a bad/cracked LCD and just swap over your good "glas" part.