27" Thunderbolt Display Issue?

SMMRepair

Member
I'm working on a 27" Thunderbolt display that loses backlight intermittently. It will work fine for a few hours, then the backlight goes out without warning. The image is still there, as I can see it very faintly if I shine a light onto the LCD (a lot tougher to make out than a MBP for sure).

I know a ton of people had issues with these things several years back; I already installed the firmware update(s) for the display, but the issue persists. Without any schematic or boardview--not to mention the incredible difficulty of somehow managing to measure voltages with the thing powered on and the LCD connected--I was hoping maybe someone had knowledge of any "common issues" that would cause this. The display powers on perfectly fine (can hear volume, USB ports work, etc), it just has a backlight failure sometimes. If left alone for several hours, it works fine for ~30 minutes initially, then backlight fails.

Any ideas?
 
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SMMRepair

Member
I'd even be fine if there's somewhere I can connect 3.3v to and have the backlight be at full-brightness at all times. I don't care about dimming. Full-brightness would be loads better than zero-brightness.
 

dukefawks

Administrator
No idea. Only thing I have done to one of these is replace the cable. You can try and connect a regular thunderbolt cable straight to the board, there is a standard connector on the board inside. Besides that I cannot help as there is no schematics and I have none of them here.
 
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