"Some say rust and electronics don't go together. Some say you must properly ground old electronics. I say that having a ungrounded, old, rusty 1300 RPM propeller near my head is better than being hot!"
Better you than me, buddy!
From the submitter: I bought this microwave oven for R$ 20 to fix it and use. Unfortunately, it is IMPOSSIBLE to find the keyboard membrane in Brazil. In USA, just the membrane costs $80!!! So I traced the keyboard circuit and made a new keyboard for it :)