How to replace 12H controller

[Nicholas Chang]

Hi All:
Our 12H suddenly restart, the LCD display init 0 to 90 and go back to init 0, repeatly.
I shutdown the 12H , pull out controller x then restart 12H. It startup normally with single controller Y.
Now we want to replace the controller X with another 12H which is not using anymore.
What's the procedule? Should I "clean" the contrller's NVRAM first? Please help!
thanks in advance. points is waiting