Modern Electronics (was Re: List charter mods & headcount... ; - test-drb@ccmp.vtda.org

23 Jun 2004

...
 From: ard(a)p850ug1.demon.co.uk

   I know
how, just about every part of, a microwave oven works and  
 Then you'll know why the HV supply is almost invariably voltage
 doubled AC and not rectified and smothed DC. 
I know it is (the magnetron itself is one of the diodes in the doubler, 
along with one capacitor and a semiconductor diode), but I don't actually 
know _why_. Presumably it's to simplify the insulation of the transformer 
or something.

-tony

Oops
 I missed this question. Tony is right. Also, once the
magnetron gets to the threshold voltage, it likes to
run at a constant volage. The capacitor source is
better at supplying this as part of the sine wave.
If you try to feed it with a fixed voltage, it will
destroy the tube. The capacitor works like a current
limiting resistor without the power loss.
Dwight