For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
I have a 21.5" iMac 820-4668. It will boot most of the way. It get to about 50 percent at normal speed. Then take a couple minutes to get all the way to 100% but will never finish booting. I have tried multiple clean installs on multiple drives.