Whirlpool microwave failed with shorted transformer.
I found another (older but same power) Whirlpool in working order but with a component in it that I've never seen in any other oven:
In addition to the usual capacitor/diode voltage doubler arrangement, this unit has a second (double-)diode across the capacitor terminals. It is the same shape/size/color as the other diode but has a symbol printed on it that looks like two diodes connected cathode to cathode (and the anodes going to the cap. terminals) with one of the two diode symbols being smaller than the other (1.5kV PRV) and one being 6kV PRV. The part number is 2X062H/SK5822 and it's listed as a protection diode.
Why would my broken oven (and others that I have worked on) not have this component while the oven that I scrounged the transformer from have it?
Microwave ovens use a fairly strange halfwave rectifier arrangement, and a consequence of this is that if the rectifier goes S/C it may not blow the fuse - and this will burn the transformer out. The purpose of the protection diode is to go S/C if the rectifier does - and this then guarantees to blow the fuse and save the transformer.
During normal working it does nothing, and older ovens didn't have them fitted.
To be honest they are a pain, they often go S/C for no particular reason.
I've already told you - if the rectifier goes short, the protection diode does as well, and blows the fuse. Without the protection diode if the rectifier fails it may kill the transformer.
Hi, been doing repairs on Microwaves for a while now and although I can test nd diagnose various faulty components I don't understand what they are there for, like the diode on the microwave.
The diode that goes from the capacitor to ground, whats it's purpose?
Hi, been doing repairs on Microwaves for a while now and although I can test nd diagnose various faulty components I don't understand what they are there for, like the diode on the microwave.
The diode that goes from the capacitor to ground, whats it's purpose?
That's the rectifier - the protection diode (where fitted) is across the capacitor.
However, if you don't know what the rectifier is, you shouldn't be attempting repairs to microwave ovens, the most dangerous domestic electrical item there is.