Chosen Solution
Hi guys, I’m struggling very hard to get this Mac to work again. The screen got broken and since then the Mac sat around for a few months before I had the chance to get it. I opened it up to check the inside of it which looks totally fine (just a bit of dust). As the screen is broken LED 1, 2 and 3 should light up normally. Instead only LED 1 is lit up and the others are off. The Mac basically turns on as the CPU Fan is spinning at full speed. I’ve checked all cables (disassembled it like 6 times already), applied new thermal paste in the process and rebuild it all again. Sadly I don’t have a spare PSU or Logic board. Can anyone help me?
If the fan is racing it’s safe to say the power supply is working as the SMC logic is doing what it should be trying to keep the system cool as the thermal sensors in the display have been disconnected so the system goes into Safe Mode. Did you get a new display yet? Your system will need it to work properly. So looking at the onboard diagnostic LED’s which you are still having problems LED 2 - Indicates that computer is turned on. This LED will be ON as long as computer is turned on (but is not asleep) and power supply and voltage regulators are working correctly. I think given the fact SMC is working (fan racing) the onboard VRM’s have an issue powering the CPU. As you replaced the thermal paste I’m suspecting the CPU chip is not properly seated or the one or more of the socket pins are bent. Did you replace the chip with another? Then its the wrong CPU. LED 3 - Indicates that computer and graphic process unit (GPU) are communicating. This LED will be ON when computer is communicating properly with the GPU. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the backup battery (on back of logic board) may need to be reseated, or the logic board may require replacement. This won’t happen until LED #2 has passed LED 4 - Indicates that computer and LCD panel are communicating. This LED will be ON when computer is turned on and video signal is being generated. If LED 4 is ON and there is no image on display, then the LCD panel or the cables between LCD and logic board might be installed incorrectly, or need replacement. This won’t happen until LED 2 & 3 have passed and you have reconnected the LCD to your system via the extension cables or directly.
