A genuine Variac typically sells for more today ($35-$50) than it did when it was first introduced in the mid-1930s by General Radio. ?
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In 1976 I was built my first computer, an S-100 system, from scratch. All of the S-100 cards required +8VDC. My motherboard had 12 S-100 card slots and it was not uncommon to have all 12 slots occupied in those days when 8KB of static RAM was typically what you would find on an S-100 memory card.
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+8VDC at 20 amps was not readily available from commonly available transformers, and space was at a premium in the portable case I built for my system. I could not find a transformer that met the power and space requirements for next to no cost. What to do? While I was looking through my parts boxes I came across a small form (120V 3 Amp PowerStat) and realized that the 120V winding was the perfect 120V transformer primary I needed. And because the core is a toroid I could wind as many turns as I needed around it to make my secondary output any voltage I wanted.
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I removed the rotor and wound mylar electrical tape around the primary to prevent anything from touching the exposed copper where the rotor brush rotates across it. Next I ran the heaviest gauge magnet wire I had through the core enough times until I got 8V at 20 amps out of my full wave rectifier / filter capacitor. I soldered taps on the primary above and below the 120V winding to allow for Hi and Lo line voltage situations just like my Tek 453 could do.
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My problem was solved for next to nothing thanks to those great Variacs.
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I still have plenty of uses for my metered Variac to this day. There is just nothing else like it.
