Chosen Solution
More information: Some time ago I tried to repair my dad’s 2007 iMac (20” I think) but it didn’t go so well. My goal was to replace the SATA cable for the hard drive and upgrade the CPU. I installed the CPU with success, but the cable wouldn’t fit in. That’s not what I’m worried abut right now, though. When trying to power it on after re-assembly, the fans ramp up to max speed, and the screen is blank. I’ve tried resetting th SMC and all that stuff, but to no avail. I really want to get this machine working again, any solutions? Edit 1: 1/13/2022 The iMac now turns on and is fully functional. The problem was a disconnected cable on the back of the motherboard, hence me not noticing it on the first look-through. Edit 2: 1/14/2022 It was the CPU Heatsink heat sensor for anyone that cares.
SMC thinks you have a problem as such it will ramp up the fam to make sure the system doesn’t over heat. You likely forgot to connect one of the cables to the logic board or something is damaged. So I would review this guide to make sure everything is connected up properly and if you see something thats damages or just doesn’t look good take a nice clear picture so you can post it here for us to see iMac Intel 20" EMC 2133 and 2210 Logic Board Replacement and here’s how to post a picture in your question Adding images to an existing question
