Fw: IT-28 Capacitor Tester question

[Sandy and Kees Talen]

It's a nice capacitor tester, Dave and I like the ease of use. Although I
own
better capacitor testers like the military ZM-11, I generally USE the
IT-28.

The leakage is measured by looking at the current with various voltages
applied (knob on the right). A leaky capacitor will show as the eye
partially
closed or closed. There is a  different "fail current" depending if the
capacitor
is an electrolytic or a small value mica, ceramic, etc. For electrolytics
the eye
just starts to close when there is a current flow of MILLIamps. For small

capacitors ( .001 mfd for example)  the eye will start to close when a
current
flow of around one MICROamp or more is detected.

Relative to tube circuits.............
Leaky capacitors in bypass circuits will cause lowered screen, etc
voltage
and consume power. Leaky coupling capacitors will change the bias levels
of the grid being driven. Leaky electrolytics in power supplies will
cause poor
filtering (not a clean DC level) and will consume power, sometimes
breaking
down further due to the heat generated.

You can also use the IT-28 to "reform" loose electrolytic by increasing
the voltage
until the eye closes, leave it until the eye opens, increase the voltage
again until
it closes, etc. Be sure to not exceed the capacitor rated voltage.

73s  Kees K5BCQ

--------- Forwarded message ----------
From: David Simmons <dsimmons at MACROMEDIA.COM>
To: HEATH at LISTSERV.TEMPE.GOV
Date: Tue, 18 Dec 2001 14:53:42 -0800
Subject: IT-28 Capacitor Tester question
Message-ID:
<A501E8FB4F4D5A4786855C01686A827A0793F713 at ex-600town-02.macromedia.com>

I recently dusted off my IT-28 capacitor checker and was trying to figure
out how it works.  The test for capacitor value seems to be simple
enough, but I can't figure out the leakage test.

Can anyone enlighten me on how that works, or what the magic-eye tube
indication for capacitor leaks would look like ?

Thanks,

 - Dave
 KQ6RL

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