microwave repair

[Dan K]

My microwave died and I found a shorted capacitor. Replacing the 0.9 uf

2300 vac capacitor (+/- 3%) with a 1.0 uf 2100 vac capacitor got the oven working again with no noticeable difference from before. Can someone tell me what changing from 0.9 to 1 uf will do to this circuit? Better yet, tell me what the capacitor is doing? Its connected to the transformer on one side and to a diode anode on the other. The magnetron connects to the diode anode also. The diode cathode goes to gnd. Is this some sort of voltage doubler? Looks to me like its a short circuit to ground for all the positive half cycles out of the transformer, so an explanation would be nice. Also the capacitor is +/- 3% which I've never seen before, being more familiar with +/- 10% or even +/- 20%. Why so tight on the tolerance?

[glenn P]

It's a half-wave voltage doubler circuit.

The value you installed shouldn't present a problem, even though it is outside the original spec. The Voltage rating IS critical, as you probably have guessed.

I hope you shorted that cap with a very well insulated screwdriver before you pulled it.....

[glenn P]

Sorry, I just remembered you said it was short already!~) I hope you shorted it anyway before you measured it, is what I meant to say!