Question about the kernel_task process and a burnt chip on the logic board

Hi all. First time here. I got tasked with fixing my sisters dead iMac late 2012. It had a cracked screen with no display but you can hear it boot up and ping it. There's no shares or any Remote access set up..

I got the replacement fused glass to LCD and everything was great until the new "apparently cheap" adhesive didn't hold the display to the case. It just fell off and pulled the ribbons out with it. Don't let me leave out that it hit a chair falling to the floor and cracked it. anyways.

Here's my issue. Since the ribbons were so ruffly yanked off the logic board I checked them over and they and the connections on the board seemed fine. I reconnected everything and he LCD did not turn on. I also smelled some burning. I immediately pulled the power. You will see the little melted chip in the attached pic. Does anyone know what that's for and what it controls? I was shocked since there's only one way to connect the cables. ?????

Here's the status.

When the system is off the CPU fan blowing at 100%. We I turn the system on the fan stops and it slowly works it's way back to 100% when the startup status bar is at 50% under the white Apple. The "Kernel_Task" process is hitting the CPU at 400%. I'm able to see this with a thunderbolt to HDMI adapter connected to a 32" LCD TV I use as a monitor. The system is fine but too slow due to this process that's taking up the CPU. Anything thoughts?

Thank you,
Steve

Welcome to the forum. I'm not the totally expert on logic boards, but I'd say, "She's dead, Jim." (Actually Steve, I know). Boards that are that severely burned are very difficult to repair and it looks like the burnt chip is surface mounted, which is a soldering job not for the weak of heart. Also the cables, although they may LOOK ok, are probably toast as well. The "wires" in those things are very, very small and easily broken just in normal handling, much less in what happened to you. Finally, when one chip goes "blooey" like that, it tends to take out other components up and down stream as it dies, all of which may be why the kernel task is running away. It's waiting for a reply that is never going to come. All that said, I'd call it done and move on. If you want to get it going again, you may have to get a new board and cables. However, there are a couple of technicians here who may have other opinions. I tried surface soldering once, won't do that again.

MacInWin said:

Finally, when one chip goes "blooey" like that, it tends to take out other components up and down stream as it dies, all of which may be why the kernel task is running away. It's waiting for a reply that is never going to come.

Click to expand...

Without a specific error message, this is what makes kernel related issues difficult to pin down. Given that the kernel is basically the brain of an operating system, responsible for managing a lot of hardware and particularly, how it all works together, it oversees a lot of different and connected hardware. If, and it sounds as if this is the case, you now have multiple points of failure, it's impossible to know what's causing it to panic. As MacInWin suggested, unless you can get all hardware working (or at least all essential hardware), this may be a very difficult if not impossible thing to figure out.

ManInWin & vansmith thanks for the replies. I'm actually using the iMac to write this email now. The fan is blowing hard and I'm sure a new logic board will be ordered soon. Im going to leave off the glass and LCD. I will continue to use the LED TV instead. it works great and saves desktop space. i don't mind spending $400 for the logic board. My sister doesn't want to spend any more money so I'm happy to keep it. Thanks for the feedback. I always wanted a Mac.
Steve