Measuring Capacitors at the Birth of Rock and Roll
The late 1950s [Bill Haley], [Elvis Presley], and [Little Richard] were building a new kind of music. Meanwhile, electronic hobbyists were building their own gear from Heathkit. A lot of that gear shows you how far we’ve come in less than a century. [Jeff Tranter’s] YouTube channel is a great way to look at a lot of old Heathkit gear, including this really interesting “direct reading capacity meter.” You can see the video, below.
Measuring capacitance these days is easy. Many digital multimeters have that function. However, those didn’t exist in the 1950s–at least, not in the way we know them. The CM-1 weighed 5 pounds, had several tubes, and cost what would equate to $250 in today’s prices. Unlike other instruments of the day, though, the capacitance was read directly off a large analog meter (hence, the name). You didn’t have to interpret readings using a nomograph or move a knob to balance a bridge and read the knob’s position.
[Jeff] doesn’t just look at the CM-1, he explains how it measures capacitance by rectifying a pulse generated by the capacitor. The average value is proportional to the capacitor’s value, and [Jeff] shows you on the scope what’s going on inside. You can pick up a lot of good information, especially if you are interested in old gear. For example, do you know what a chicken head knob is? If you don’t, definitely watch the video!
If you have any interest in vintage gear, [Jeff’s] entire channel is worth a look. He also does a lot of retrocomputing projects and documents them in great detail. If you aren’t old enough to remember Heathkit in its glory days, it is hard to grasp the scope of it. They made everything including TVs, ham radio gear, robots, computers, terminals, and–of course–test equipment. All in kit form with meticulously detailed manuals that no one else has ever quite recreated. Take a look at some of [Jeff’s] videos and you’ll see what we mean.
Filed under: classic hacks, teardown
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