How do I know if my iMac has a bad motherboard?

If your iMac has a bad motherboard, there are a lot of symptoms that can appear to look like several different problems.  If your computer is not booting up properly, is freezing or turning off randomly, or slowing down drastically, there are a few things that may be wrong with it, including a bad motherboard.  Don’t worry though, we’re here to diagnose before we fix anything, so we’ll make sure if it’s a bad motherboard before we replace anything!