Vintage Digital Frequency Meter Teardown

You think of digital displays as modern, but the idea isn’t that new. We had clocks, for example, with wheels and flip digits for years. The Racal frequency counter that [Thomas Scherrer] is playing with in the video below has columns of digits with lamps behind them. You just need the right plastic and ten lightbulbs per digit, and you are in business. Easy enough to accomplish in 1962.

Inside the box was surprising. The stack of PC boards looks more like a minicomputer than a piece of test gear. There were a few novel items inside, too, ranging from a glass-encapsulated crystal to an interesting method of selecting the line voltage.

The design seemed thoughtful. There was even a spot for spare bulbs for use when they inevitably blew out. The device has seen a few previous repairs, it seems. But with a little coaxing, it still does its job.

As high-tech as this might have been in 1962, the top range was supposed to be 300 kHz. Turns out, it was able to do quite a bit more than that. Overall, a great piece of engineering for its day and a seemingly rare instrument.

Of course, this wasn’t the only frequency counter to use this kind of display. The lights are a bit more elegant than using meters.

4 thoughts on “Vintage Digital Frequency Meter Teardown

  1. More information on this equipment is available on the internet, including schamatics. Transistors are germanium PNP. Flipflops used 2 transistors, resistors and speedup capacitors, and diodes. A few years later, a Nixie (?) display version was available.

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