Capacitor testers

[Christian Fandt]

Best tester huh? Talk about subjective opinions ;-)

I like my military ZM-3A/U capacitor analyzer. Very quick to use and quite
accurate for testing values. Got it for $10 at a hamfest. Was a bargain,
IMO. Last sale of the day for the fellow before we both left just ahead of
the gates closing behind. Originally marked $30. It should be found for up
to $50 or so.

Leakage test meter resolution rather low but I use a combination of my
Heath IP-32 variable 400 volt power supply (See! I *do* use Heath gear to
test caps! ;-) a 30,000 ohm 5 watt resistor in series with the cap under
test and a DVM connected across the resisitor. Very accurate leakage
measurements on any type cap. More importantly, this setup allows me to
reform electrolytics in a controlled manner. Motor start caps are a little
wierd to leakage test though. I've got a remotely-controlled Bertran 1KV
power supply which I will begin to use as it can let me test caps which
normally operate up towards the 500-600 volt level in certain early TV's,
etc. Also, I could lash it up to a computer which has an A/D conversion
board to measure voltage across the resisitor. With programming, the system
could automatically ramp the voltage up to the max working voltage of a cap
while monitoring the current through the resistor (current calculated from
the voltage measured across the resistor divided by 30,000 ohms) to keep it
at a reasonable reform rate and display leakage value directly. But I
digress . . .

There's a military ZM-11 L-C bridge but I don't know much about that
critter yet. Haven't found one around here yet.

I've got an early Heath cap tester (probably a C-3, it's brown and no model
shown on front panel) but it needs electrical restoration first. Generally
poor accuracy but for general purposes like many folks would use it for,
it's in the ballpark.

There's a Heath IM-series cap tester I heard mentioned here which sounds
appealing. Could anyone give a clearer description of it for us? I want to
eventually find other Heath cap testers to add to the Heathkit collection
whenever I finish my Bachelor's degree (no, I'm not a young squirt, I'm 46)
and get another engineering job ($$).

I have an EICO 955 capacitor tester but it's a somewhat simpler unit than
even the C-3.

I have a Mallory CRT-1 capacitor-resistor tester on the bench now under
restoration. This looks like a very good piece of gear. Being designed and
made by a major capacitor manufacturer back in the mid-50's it _ought_ to
be a fairly good piece. Has a good leakage test section which has a
variable voltage up to ~500 VDC and uses a magic eye tube which should make
it somewhat sensitive in checking leakage like the Heath C-3 *may* be.
Construction reasonably good for a mid-50's service shop-level piece of
test gear.

The CRT-1 worked sorta well before being dismantled but the 6 wax coated
paper caps had become rather leaky and I found about half the resistors are
out of their tolerance range. The value evaluation section was fairly
accurate on a couple of ranges in which its reference caps hadn't leaked or
the corresponding resistor wasn't way off. 4 of the 5 electrolytics were
not very leaky at all though.

A Jackson 691 capacitor tester is another unit I like well. On par with the
Mallory with regard to potential accuracy, functionality, design and
construction. Magic eye tube bridge display. Has an accurate pointer-scale
arrangement which has about 355 degree rotation across two linked scales
(hafta see it to get an idea of what I mean) and switchable leakage test
voltages in 8 levels from 3 VDC to 500 VDC. It used to be my mainline unit
'til it went flakey. Likely one or more paper caps have gone south as I'd
previously changed all the electrolytics. In the que for restoration someday.

Ultimate boatanchor cap tester is a 60 pound General Radio 1683 Automatic
RLC bridge setting next to my bench. I use that occasionally but the ~25 lb
ZM-3A/U is more "portable".

Oh, BTW I've got a Sprague TO-3 capacitor tester too. _That_ thing surely
needs restoration. Looks like it sat in a damp basement for some years
before I bought it. I hear these TO-series units were pretty good units.
The model variants go up to TO-6 or -7 produced from the late 40's into the
60's.

Somewhere here you may have gotten the idea that I like to collect and even
use test gear ;-)

Regards,  Chris
-- --

Upon the date 04:31 PM 12/17/99 -0600, Mike Slack said something like:
>I've read with interest the thread on reforming electrolytic capacitors and
>I've decided I need to find me a good cap tester.  I'm sure the Greenies
>will weigh in heavily on this one, but I want to know what you reformers
>think is the best tester out there.  I'll sit back and let you sages have
>the bandwidth.  Mike KD5ICD


Christian Fandt,         Electronic/Electrical Historian
Jamestown, NY  USA      cfandt at netsync.net
        Member of Antique Wireless Association
        URL: http://www.antiquewireless.org/

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