Re: Another H1812 source

zonn@zonn.com wrote:

> On Sun, 21 Jul 2002 00:27:06 -0500, Joe Bachmann
> <joe.bachmann@newmail.net>
> wrote:
>
>> Rodger,
>>
>> Good point, that probably wouldn't be enough for a HV diode that we
>> are using.
>> But, the drawing you gave will only test that the diode is conducting one
>> direction or the other. Using that method the diode could be shorted.
>> So, we
>> would need to use DC to run this, not AC. Just adding in a simple bridge
>> rectifier with a decent filter cap should be enough. You will of
>> course need to
>> test the diode both directions in the circuit.
>
>
> This is what AC does for you. As Rodger stated a good diode would only
> light
> one side of the neon bulb. A shorted (or leaky) diode would light both
> sides,
> an open diode would light neither. You can't just look at if the light
> is lit
> or not, you have to look at *how* the light is lit.
>
> Though as a disclaimer I've never used a neon light to test a HV diode.
>
> -Zonn

Exactly. A neon bulb has two electrodes and they glow independently
depending on polarity. On AC it APPEARS that both sides glow, but a
high-speed camera would prove that they take turns. When supplied with
DC (as in our little tester) only one side will glow. Connecting the
diode in the opposite polarity will change which electrode glows.

Neon bulbs are interesting. You don't even have to connect them to make
them glow, an RF field will do just as well. So if you buy more than
one you can always tape the other to a dowel and use it to tell you if a
flyback is running---just hold it close and it will glow big-time. You
might even be able to tape one to a flyback so you have a power indicator.

You can even use the glow tubes out of bad fluorescent starters for the
flyback testers (NOT for the diode tester!). Use the tube out of an
FS-2 or FS-5 if you want orange, an FS-4 or FS-12 will give you purplish
blue. You can even break the leads off, it makes no difference.

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Received on Sun Jul 21 00:30:34 2002