Unit worked fine except it would not heat

Had to take unit off wall and disassemble the main casing.then disconnected the wires from the magnetron.took the mounting nuts off but wasn't able to remove the magnetron until I loosened the transformer out of the way .Then it came out easy.Installed the magnetron ,tightened the nuts,installed the transformer back in, connected the the wires back on and installed the casing on ,screwed the screws and got help to install the unit to the wall again.....Tested the unit before putting back on the wall to make sure it heated....The parts were exac same type and wasn't too hard to do...