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variacs:


A variac is a 120vac transformer with a continuous variable tap for the secondary winding. It allows smooth
adjustment of the output voltage without affecting frequency, and often comes with a built-in voltmeter so you
can tell what voltage is being developed. The winding often extends a bit past the outside leg, allowing for
an output range of 0 to 130 volts AC. Since it's just tapping the winding, it doesn't provide any isolation
from commercial power like you'd get with a traditional dual-winding transformer.

One handy use for these is to gradually power up old gear that contains electrolytic capacitors that may require
"reforming". Quickly powering up old capacitors can lead to catastrophic failure. They can literally blow up,
spraying the area with wet, hot, and quite smelly bits of paper confetti. This Satan's Confetti quickly dries,
usually before you can get the equipment taken apart, and solidifies into a sort of paper mache', that takes
forever to dig out of the gear with pliers, screwdrivers, and tweezers. (as me how I know!)

I've owned an old one of these for years, old enough that it doesn't have a ground pin, but I just picked up a
newer unit that looks like it qualifies as "new old stock". It's considerably larger, is rated for up to 2kva,
has a built-in volt-meter, and comes with this snazzy red paint job.



Circuit Specialists TDGC-2KVA



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last updated 05/16/2025 at 12:14:35 by make_www_index.command version 2025.05.13.A