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A high-frequency (HF) start box is a device used in AC arc welding that allows you to start an arc welder without having to “scratch-start” the arc. You used to be able to buy such an add-on device; apparently, they’re now hard to find. William F. Dudley Jr. decided to build his own and shares the details on his project page.

[As with all high-voltage projects, the usual warnings apply (as in: don’t try this at home unless you’re familiar with HF and know what you’re doing).]

High-Frequency Start Box