Hi all,

I have a Sharp carousel microwave probably 10+ years old and the fuse blew in. Replaced it but when pressing Start to cook food, it blows again.

I've tested the HV cap and magnetron with a multimeter and the diode by placing it in a 12V circuit, all seem ok but you never know...

I disconnect the HV transformer, pressed Start and the fuse didn't blow.
Then I connect the primary winding and disconnect the secondary winding / magnetron filament and it works.
Next I connect the secondary winding to the HV cap and it blows (maybe cap is shorted at high voltage?)
Remove the HV diode, connect the magnetron filaments and it works. Re-connect the diode and it blows.

So something about connecting the diode is making the fuse blow. I've tried making a diode with smaller diodes in series to make 7-8kV combined but even that blows the fuse.

I'm not too sure what else to try, do you think the transformer or cap is bad?

Thanks for your time,
Alex

When both leads to the magnetron were disconnected, I tested them and they had continuity to each other.
Either magnetron lead to ground had no continuity.

If I remove the magnetron completely, it still blows the fuse. If I then remove the HV diode, it doesn't blow (since the HV side has no connection to ground)

I'm thinking about removing the HV diode and just connecting the HV to the cap directly and see if the fuse blows, if so then that would mean that the cap must be shorted at high voltages?