wrote in message ...
super-strong magnets which my grandkids really enjoy. But I've also
been
saving the transformers, diodes, fans, and capacitors, with the ultimate
goal of making a high-voltage power supply for a homebrew amplifier. So,
without any high-tech equipment, how might those diodes be tested?
--
--Myron A. Calhoun.


Those transformers had magnetic shunts that limited the current they can
deliver. There's been some discussion about using them in the ham press
over the past several years. I think the inagural issue of Communications
Quarterly covered it in some detail. You'll probably have to do some simple
mechanical mods to the power transformers.

Pete

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?"
================================
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

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

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

You need to build a hi-pot tester. Schematics are found using a search
engine. Basically, you take a high voltage dc and connect it through a very
high resistance and a microammeter to the device to be tested. Then, you
crank up the variac to see when the device fails. Current will be limited
so you will not damage it.

You can use one of your discarded microwave units for the voltage source,
which means that you will be looking for a variac and a couple of low
current meters along the road to complete your test equipment wish list.

Colin K7FM

In article , wrote:
Please be aware of that fact that high voltage multi-junction diodes for
microwave ovens are available for next to nothing and can be a good
substitute for long diode strings with a single element.

Now THAT's a good idea! Any idea how to test USED ones?

Plug 'em into the AC power line, measure DC out. The voltage drop on them
is too high to use the diode setting on most meters.

On my morning school-bus route, I see about one discarded microwave oven
per month, and if they're not too far from the bus-barn, I return later,
"liberate" them from the "sidewalk store" and tear them apart for their
super-strong magnets which my grandkids really enjoy. But I've also been
saving the transformers, diodes, fans, and capacitors, with the ultimate
goal of making a high-voltage power supply for a homebrew amplifier. So,
without any high-tech equipment, how might those diodes be tested?

The transformer is the BEST PART.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."