30 microwaves were used in this circuits DIY project where the creator shows you how to make a massive 30kV voltage multiplier from scrapped microwave parts. This might be useful if you have a need for some serious voltage power for building projects like a high voltage plasma ball or even a high voltage chair. Also see this DIY on how to make high voltage supply in 5 minutes.
There is a high voltage transformer, capacitor and diode in every microwave. During my days at the dump I demolished a total of almost 50 microwaves for the transformers. Of course I also took the capacitors and diodes, but didn’t have any purpose for them yet. Now I used them to create this cascade. Loud bangs during flashovers and a few nice pictures.