The Cardmatic line of tube testers were
introduced in the 1950s by the well known and respected test gear
manufacturer Hickok. They were unique in that instead of using
massive numbers of switches, dials,
and tube sockets, they used punched cards. The idea was to save
time
and eliminate mistakes, and the idea worked. This line of testers
was
also produced for the military and for Western Electric, and those are
the
ones we are most interested in. Not only did they represent the
state
of the art in tube tester design, but they were also built like a tank,
meant
to survive a war.
The biggest problem with this tube tester
concept was the cards themselves. They were usually housed in a
separate container
the same size as the tester. If a new tube came out and you
wanted
to be able to test it, you had to order a card from Hickok (or
figure
out how to punch your own). Eventually the tester lost some of
its
attractiveness because you found yourself having to use a second tester
every
time you didn't have the right card. Over the years many surplus
testers
got orphaned from their card set and thus were rendered useless.
This
is sad, because the tester itself is an ingenious design.
Imagine having on your test bench:
A bank of tube sockets, all wired
together, that covers every common tube base.
A filament power supply that can be set
to
any voltage up to 120V in .1V increments.
A regulated B+ power supply that can be
set
to any voltage up to 260V in 10V increments.
A very accurate current meter that can
be set
for any full scale reading up to 500mA in 1 mA increments.
A gm bridge circuit to measure the
amplified
plate signal current.
A precision decade resistor box that can
be
set to any resistance up to 70K in 10 ohm increments.
A very well regulated .222VAC signal
voltage
supply for checking amplification (transconductance).
A separate power supply providing a
regulated
+ and - 150 Volts.
A transformer providing 500VAC, center
tapped.
A patch panel that connects everything
together in any combination desired.
This would be a nice setup indeed for a test
bench. But all of this and more is contained within the Cardmatic
tube tester. Now, in the 21st century, we can add a computer to
the bench and turn the Cardmatic into something much more than just a
good tube tester.
More technical details about the Cardmatic
can be
found in the White
Paper.
Click here for
some
pictures.