Product model: iMac 27 2017 iMac18.3
Problem Status:
Last week, I removed the motherboard and replaced Fushion Drive, I use WD M.2 Nvme ssd and removed the HDD, the screen was fixed with tape, and the normal boot is completely fine.
I took down the screen and add Micron 2.5-inch ssd today.
I thought it would be better to remove the screen have better cooling.
I used the Studio Display to be the iMac external screen.
After that, the kernel_task took up too much CPU usage, and then I shut down the computer and installed the screen back, but couldn't turn it on.
In the later test
1.Built-in screen is unplugged and the Studio display is connected, it can be turned on but the CPU is occupied.
video0
2.When the built-in screen is installed and turned on, it will keep repeating the boot sound and cannot be turned on.
video1 video2
3.The built-in screen is replaced by other iMac it can light up normally.
View attachment 2027523
產品型號：iMac 27 2017 iMac18.3
問題狀況：
上禮拜拆除主機板更換上，WD M.2 Nvme ssd 並拆除HDD，螢幕膠帶固定，正常開機完全沒問題。
前幾天拿下螢幕，跟換上美光2.5寸 sad，想說移除螢幕散熱會比較好，外接上Studio Display上使用把iMac當主機，開機後風扇狂轉，操作上非常緩慢，打開活動監視器, kernel_task超佔CPU用量，之後就關機要把螢幕給裝回去，但是裝回去後反而無法開機了。
後面測試只要拔掉內置螢幕接上Studio display ，可以開機但是CPU都被佔用掉了。
內置螢幕裝回去開機會一直重複開機聲，無法開機。
內置螢幕更換到其他imac上可以正常點亮。
請問這是主機板問題，但是可以正常開機。
Problem Status:
Last week, I removed the motherboard and replaced Fushion Drive, I use WD M.2 Nvme ssd and removed the HDD, the screen was fixed with tape, and the normal boot is completely fine.
I took down the screen and add Micron 2.5-inch ssd today.
I thought it would be better to remove the screen have better cooling.
I used the Studio Display to be the iMac external screen.
After that, the kernel_task took up too much CPU usage, and then I shut down the computer and installed the screen back, but couldn't turn it on.
In the later test
1.Built-in screen is unplugged and the Studio display is connected, it can be turned on but the CPU is occupied.
video0
2.When the built-in screen is installed and turned on, it will keep repeating the boot sound and cannot be turned on.
video1 video2
3.The built-in screen is replaced by other iMac it can light up normally.
View attachment 2027523
產品型號：iMac 27 2017 iMac18.3
問題狀況：
上禮拜拆除主機板更換上，WD M.2 Nvme ssd 並拆除HDD，螢幕膠帶固定，正常開機完全沒問題。
前幾天拿下螢幕，跟換上美光2.5寸 sad，想說移除螢幕散熱會比較好，外接上Studio Display上使用把iMac當主機，開機後風扇狂轉，操作上非常緩慢，打開活動監視器, kernel_task超佔CPU用量，之後就關機要把螢幕給裝回去，但是裝回去後反而無法開機了。
後面測試只要拔掉內置螢幕接上Studio display ，可以開機但是CPU都被佔用掉了。
內置螢幕裝回去開機會一直重複開機聲，無法開機。
內置螢幕更換到其他imac上可以正常點亮。
請問這是主機板問題，但是可以正常開機。