Original poster: Ed Phillips <evp@xxxxxxxxxxx> Tesla list wrote:
Original poster: Mark Fergerson <mfergerson1@xxxxxxx>I recently acquired a type 10B Powerstat for US$1.00 which is a steal, but when I got it home I noticed that the wiper button is missing. Can I just whittle a new one from say a D-cell center carbon, or would that be too resistive? Any better suggestions before I go ahead and burn the house down?TIA Mark L. Fergerson
Better to go to a motor shop and find a carbon brush as close as you can to the size you need, then file it down. The "carbon" from a flashlight cell tends to be very contaminated. The brush is intended to have enough resistance so that the power lost do to the current created when it shorts adjacent turns of the variac is acceptably low.
Ed