The HV diode cannot be properly checked with an ohm meter. The
breakover voltage required is too great. If the diode is opened there
is no way to know wiithout doing a proper voltage check. For this you
will require the proper HV probe. If the diode is shorted the HV
transformer would be overloading and most likely the fuse will be
blown.

Common causes of failures as what you are describing are from the
diode being opened, transformer failure filter capacitor failure, and
or magnetron failure.

Take care for safety issues in dealing with the high voltage area of a
microwave oven.

Jerry G.




On Apr 24, 10:25*pm, "ManhattanMan" wrote:
4 year old sharp microwave that overnight decided it'd do everything but
heat.

All functions normal, except heat. *There is 120V applied to the HV
transformer primary, secondary measures 150 ohm, filament on both
transformer and magnetron shows negligible ohms, diode tests good on back
voltage, HV cap appears OK, magnatron does get very hot after a couple of
ten second tests...... *?????

I've had several with bad micro switches, HV cap, etc., but this one does
everything but heat for no reason.....

TIA