Display light randomly shuts down
I'm gonna write down everything what happened so you can get a clear picture about the problem.
One day I've been working on the iMac and the backlight suddenly shut down. I've tried everything, but it hasn't came back. So we took it apart and checked every cable etc. concerning the LCD screen and GPU...then checked if the 4 LEDs on the motherboard are lit (yes), and anyway I've been able to see the image on the screen with a lamp pointing on it.
So I've measured what comes out from the PSU to the inverter board, and it was ok (12V), then moved to the output of the inverter board and only measures a few mVs, which seemed to me not ok. So later I went hunting for an other inverter board, and I found one at a local repair shop, but it wasn't the exact same type that's on my iMac. The one I bought was actually inside the same year model of iMacs, but I thought I have to try it out anyway.
The type of inverter my iMac had is the: Sumida 612-0094 (4 pin)
and the one I put in instead is the: V267-604HF (4 pin)
So i changed the inverter board and voila the backlight worked again. And after a while suddenly it shut down again, but i was able to wake it with a keyboard shortcut. And it happened again and again after I found out that it's not shutting off when the brightness is turned only until 5. I clean installed a new Mac OS, and it worked for 2 hours straight then it started all over again...
I took the iMac to the repair shop to check the LCD screen. They put inside an other (used) LCD screen which seemed to solve the problem. The backlight worked for 3 weeks, then it started again...
My question is: Is it possible that the inverter board is causing this issue? Or can it be, that the new (used) LCD screen is also bad? I think it's strange and I assume it's not the LCD screen itself, but maybe I'm just really unlucky? What else can cause such a behavior if it's not the inverter board?
It was the inverter board. Since installing the correct part number one everything works perfectly :)
So if anyone planning to change a broken inverter board to another one, always change it with the same part number only! Pin numbers and iMac model matching is not enough, no matter what others say ;)
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