> "tm" <No_one_h...@white-house.gov> wrote in message
>> "Wipf" <w...@ra.msstate.edu> wrote in message
>>> In article <k4ia3a$ip...@dont-email.me>, No_one_h...@white-house.gov
>>>> "Wipf" <w...@ra.msstate.edu> wrote in message
>>>> > Hi,
>>>> > I'm a lurker here and I thought I'd ask for some help. I have a few
>>>> > boards I saved from the trash that appear to be little HV supplies
>>>> > for a
>>>> > mass spectrometer. I was trying to trace through the circuit and
>>>> > could
>>>> > not figure out what these components were on the (presumably)
>>>> > multiplier
>>>> > part of the circuit. A picture is here
>>>> > http://www.flickr.com/photos/dwipf/8051484989/in/photostream
>>>> > They look like diodes but don't read as diodes on my multimeter
>>>> > (maybe
>>>> > because they are in circuit). They are marked as 00B or OOB which
>>>> > doesn't seem to be any diode code that I can find.
>>>> > Any thoughts?
>>>> > Thanks
>>>> > David
>>>> It is a HV multiplier. A X3 positive multiplier on the left side and a
>>>> negative multiplier on the right.
>>>> Look up Cockcroft-Walton multiplier on google for much more detail.
>>> Thanks, I think it is a multiplier but my question is specifically about
>>> the "diodes" marked 00B. I couldn't find any info on their specs and, in
>>> fact, don't read as diodes using my DMM.
>> They are high voltage diodes and have a large forward voltage drop. Maybe
>> up to 10 volts or so. They are made up of many series diode junctions in
>> order to get the high reverse voltage needed.
>> Try forward biasing to diode through a current limiting resistor with
>> maybe 24 volts and 10 k ohms. Measure the forward voltage drop across the
>> diode. You can do this in circuit.
> if you have a simpson 260, there is enough voltage to get the meter to
> move a bit ;)
Those little diodes don't have very many junctions so you would be right.
Some of the >10 kV diodes drop 10 -15 volts (or more) forward. I still use
my 260 but you need to be careful. It can do a pretty high current for some