Why does 20a fuse keep blowing when I power up my advantium 120 ge

Yeah pal, you've not gone deep enough yet. You'll find a power wire bare inside the unit, pull it apart and tape that wire up to stop it from grounding out and blowing the fuse.

Our unit was doing the same thing,
took it into the repair shop, they said there was nothing wrong with the unit, replace the main breaker that supplies power to microwave and try again.
Sure enough the breaker became defective, and we never had issues with it before, but now the unit has not had a single problem.

Most likely a blown fuse inside the MW. It will be on the control board or on the incoming power line inside the cabinet.

I would call GE and explain the problem It may be a glitch in that model they may be able to give you the solution

check 20a fuse or thermal cutoff(KS-2N)

remove the cover ... look on the floor of the unit near where the cord enters the cabinet.

under the outer cover on a fuse clip its a special fuse avail at hardware stores

My advantium 120 died and it has power to the oven but it does not work! does the oven have a fuse that i can change?

remove outer shell/cover, the fuse will be in a fuse holder about 1" long X 1/8" in diameter and is called a ceramic fuse,take it out,look on ends for current rating go to hardware store they have repl fuses, if the new fuse blows it could be your h.v. diode, capacitor, or the magnetron tube

Does the unit have power?If not check the back and see if ou can take off. Most unit have fuse back there.