A microwave diode is used as a mixer at microwave frequencies. You have
a microwave oven diode.


Andrew Rossmann wrote:

I have an older, 1998 GE Microwave oven. By the LG parts inside,
probably just a rebadged LG. Lately, it's tended to 'thunk' when the
magnetron turns on. A few times, it started rapidly cycling. Once, I
didn't stop it in time and it blew it's 20A fuse. Another time, just
starting normally, it tripped a circuit breaker.


Check the waveguide to make sure it doesn't have food or grease in
it, and that the cover is in good shape.


I opened it up and checked. So far, the only obvious thing I can see is
that the large diode between the transformer and ground may be open. I
get infinite resistance in both directions. I assume there is nothing
special about testing these types of diodes?


There are not regular diodes. There are a stack of diodes, and have
a higher forward voltage drop.


It's an HVR-1X diode. This appears, based on some Googling, to be very
common, and the HVR-1X3 seems to be a common replacement.

Do the symptoms I describe seem to go with the way the microwave is
acting? I'm not certain just what the true function of the diode is in
this case (I know how a diode itself works). There is also what looks
like a starter cap. It's rated at 1uF, and my meter says 1.15uF or so.


That is a common oil filled HV cap. They usually fail shorted. Look
at the tolerance ratings on it. It's likely +/- 20%, which means the
reading is OK. Also, be careful inside a microwave. It can kill you in
a heartbeat. That cap should have a bleader resistor across it. If it
fails, the cap will retain a charge that will kill you.


Do you think it's worth trying to replace it? I did buy a replacement
microwave, but regret it. It's basically the same, but has some issues I
don't like (display too far back from front, so you have to squat down
to see it while typing on the panel. Fan goes REAL fast when magnetron
off, then seems to nearly die when it's on.)


--
You can't have a sense of humor, if you have no sense.