[Amps] OT - Microwave oven diodes

Val val at vip.bg
Sat Apr 4 16:31:40 EDT 2015


The HV diodes are usually made by a string of 1kV diodes. Every 
regular silicon diode "eats" 0.6V of the passed thru forward voltage 
and a HV string may "eat" 3 or more Volts. Most of the DMMs provide 
only a lower voltage that can not "feed" a string of several diodes. 
No current flows and the DMM read an open circuit.

The HV diode can be tested in every circuit where the voltage is more 
then 10V.

By the way, it is the magnetron that most likely is failed. Check the 

73, Val LZ1VB

> My regrets to ask something much OT but
> I'm guessing the answer I need likely will
> be be from within this group.
> My Panasonic Microwave oven stopped
> working last night. There was nothing
> unusual the last time I used it, it worked
> perfectly. It's a particularly nice &
> powerful oven with many helpful bells &
> whistles and will be expensive to replace
> so if I can fix it, I'd like to.
> It accepts AC, displaying all the
> functions it should but when engaging the
> unit to heat, it stops rotating in around
> two seconds and the display defaults to
> waiting for a command.
> My first thought is an issue with the
> power supply. I located the two diodes
> number UX-F5B and can't get any reading in
> either direction with them in the circuit.
> I expected to have some reading from at
> least one of them but both show nothing on
> the Fluke.
> Data sheet here
> http://www.datasheet-pdf.com/datasheet-htm
> l/U/X/-/UX-F5B_AllegroMicrosystems.pdf.htm
> l
> or http://tinyurl.com/nkhxxc6
> I don't get a reading from the diodes in
> my HF amplifier so I guess it's the same
> issue. How do I check to see if there's a
> blown diode in this case? & of course
> there's the unknown of what initiated the
> failure.
> Off list reply if you would, I don't want
> to start an OT thread.
> Thanks & 73,
> Gary
> KA1J
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