RadioBanter - View Single Post - Equalizing resistors needed for HV diode string?

February 7th 06, 01:34 PM posted to rec.radio.amateur.boatanchors

wrote:
super-strong magnets which my grandkids really enjoy. But I've also been
... without any high-tech equipment, how might those diodes be tested?

.... You'll probably have to do some simple
mechanical mods to the power transformers.

I'm aware of (and have done) the transformer mods, but what I'm asking
now is

"without any high-tech equipment (beyond the usual ham stuff such as
resistors, VOM, etc.) how might those diodes be tested?"
================================

Well, first, you have to ask yourself, "what does a diode do?", and next
you have to ask yourself, "what is special about these diodes?" After you
answer these little questions, the answer to your big question should be
obvious.

In case it isn't, a diode is a one way valve for current, so you need a
source of current to test a diode. And second, these diodes are stacks
of diode wafers in series, so they have many forward conduction diode
voltage drops when current passes from anode to cathode.

A 9V battery, a 1K resistor, and a DVM set to measure DC volts across the
diode would do. Put the 1K resistor in series with the "+" terminal of
the 9V battery, and connect the other end of the 1K resistor to the anode
(unbanded end) of the diode, and connect the cathode (banded end) to the
"-" terminal of the battery. The DVM should show several volts across the
diode in this position. If you divide this voltage by 0.6V, and round down
to the nearest whole number, you will get the number of diode wafers in the
rectifier. Now, reverse the battery, and you should see 9V on the DVM.

If you happen upon a really HV rectifier, use 2, or more, 9V batteries.

Now, the big question that comes to my mind: If you can't figure out
how to test a diode, should you really be mucking around with a power
supply that can kill you 10 times over? I'm thinking, no... But as always,
it is something for you, and your widow to be, to decide.

-Chuck