If you grew up in the 1960s, your parents might have sent you to the local drugstore to test radio or TV vacuum tubes (“valves” in the UK). The tube tester, an imposing device with dozens of sockets and a large meter, sat on top of a cabinet with shelves of new tubes to choose from if the meter pointed to REPLACE when you plugged yours in.

The self-service tube tester was a simplified version of those used by professional technicians and the military, for which thoroughly testing a particular type of tube (of which there were hundreds) required setting multiple switches and dials—and a mistake could ruin the tube. The Hickok Cardmatic tube tester solved this with punch cards. When a card was inserted, an array of 187 switches was pressed against it. As described in the 1961 Hickok catalog: “the absence of a hole completes a particular circuit; the presence of a hole causes the circuit to remain open.”

These cards are from a set for the Cardmatic 123R, which came out in 1961; they also work in the earlier Cardmatic 123A. The 123 came with 500 cards, but more could be ordered from Hickok. Users could also create their own cards using a hole punch (see below), although since most of the 187 switches were open for a typical tube, punching the holes by hand must have been somewhat tedious.

The Cardmatic is a dynamic mutual conductance tester, which measures the tube's output current relative to AC and DC voltages applied to its inputs. (For more than a hand-waving explanation see The Valve Museum.)