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
and eliminate mistakes, and the idea worked. This line of testers
also produced for the military and for Western Electric, and those are
ones we are most interested in. Not only did they represent the
of the art in tube tester design, but they were also built like a tank,
to survive a war.
The biggest problem with this tube tester
concept was the cards themselves. They were usually housed in a
the same size as the tester. If a new tube came out and you
to be able to test it, you had to order a card from Hickok (or
out how to punch your own). Eventually the tester lost some of
attractiveness because you found yourself having to use a second tester
time you didn't have the right card. Over the years many surplus
got orphaned from their card set and thus were rendered useless.
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
any voltage up to 120V in .1V increments.
A regulated B+ power supply that can be
to any voltage up to 260V in 10V increments.
A very accurate current meter that can
for any full scale reading up to 500mA in 1 mA increments.
A gm bridge circuit to measure the
plate signal current.
A precision decade resistor box that can
set to any resistance up to 70K in 10 ohm increments.
A very well regulated .222VAC signal
supply for checking amplification (transconductance).
A separate power supply providing a
+ and - 150 Volts.
A transformer providing 500VAC, center
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
found in the White
Click here for