I built this from a old used microwave oven the first thing I did was open it up and found the Capacitor and the MOT (the transformer) it’s always near were the power cord comes into the oven.
THE FIRST THING TO DO IS SHORT OUT THE BIG CAPACITOR
DANGER THIS WILL KILL YOU IF YOU DON'T DISCHARGE IT
Discharging a high voltage capacitor
Discharging your microwave's capacitor is absolutely essential in preventing injury to your microwave, your tools, and
yourself. A capacitor stores large amounts of electricity even when your microwave is unplugged, and it must be discharged
A capacitor is discharged by creating a short circuit between each of the two capacitor terminals, and between each
terminal and the chassis. The chassis is the metal mounting (bare metal surface) of the capacitor. With your microwave unit
unplugged, touch the blade of a well insulated screwdriver to one terminal. Gently slide the screwdriver forward until it
reaches the other terminal, holding it there for a few seconds. Be aware that this often results in a loud and startling 'POP'.
Repeat this procedure in order to create a short circuit between each capacitor terminal and the chassis (bare metal
mounting plate surface). This same method can be applied to a capacitor having three, and not two, terminals.