This is a GE over the stove Advantium microwave/Convection oven with built in exhaust fan. It is working; however, there is a round knob on front that digitally controls many features of the oven, including built in convection settings. It is also used to change the amount of time you want to run the oven. The automatic 30 second button starts the oven just fine. You can press this multiple times to increase time. But the round knob raises or lowers the amount of time and is used to select other features So this is the part that is not working now. Replacing just the knob is an inexpensive repair, but I need to know if there is something else wrong, like the board inside. The other buttons give a beep when pressed, but most require the use of the round knob for more detailed control, changing any settings, clock, timer, etc, so none of that works.

I've had it for a little over 4 years. I hope this makes sense.
Thanks!