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New variacs - Powerstat 136B - 22 amps

Marco Polo

Active member
Nov 2, 2012
So the month of May is shit for me. My birthday is on the 7th but the BMV pisses all over that by demanding I fork out 50 dollars for car plates. Happy birthday, you crooks. Then my PO box fee hits, there's the monthly car payment theft, and the much more annoying car pizzo theft, a.k.a insurance. Hate. Hate my cell phone bill too, wish I could get rid of it, but it's only 30 dollars, but that is still too much. (If I paid 1 dollar per minute my monthly bill would be 10 to 15 dollars max.)

I have a Variac V5 which is useful but it's only rated at 5 amps, and it turns out that pulling arcs off MOTs push it a bit too close to its ultimate limit of death (25 amps). I think it pulled about 20 arcing a MOT but I only did it 10 seconds here, 10 seconds there, and kept fan cooling on it the whole time, so it's fine.

But I want more!

I decided I was tired of scrimping and having nothing to show for it, so I completely torpedoed my budget and bought a Superior Electric Powerstat 136B from ebay. Been looking at them off and on for a little while and the prices are all so bad. Most of them want $500+ for a dirty, used-looking one that is missing parts, ridiculous. But one seller in North Carolina claimed excellent condition and had pictures, so I took the bait. Upon receiving it, I did the initial basic tests on it... when those checked out, I took it apart and checked all the connections, windings and sliding tap for any evidence of high heat or other damage.

Nope. Seller was as good as his word. Can't help but appreciate that and I let him know it. The only thing wrong with it was that the control knob's setscrews were slightly worn/stripped and I couldn't tighten them down, otherwise it might as well be new. Except for the price, only $140 dollars. Brand new one is $1000+ and other ebayers ask way too much. I put it back together, greased the center shaft and replaced the setscrews and it works great.

But it gets better. Not 24 hours later, there was another one. This one in Canada. Similar claims, and this one had a switch box on the front, with an on/off, a neon, and a fuse. $160 due to shipping across the border. Since I torpedoed by budget already, why not drop a couple depth charges on it too? So I got that one as well.

Initial testing on this one was less encouraging, it appeared completely dead. The cord was 16 AWG, in good shape, but way too small. The switch was fairly cheap, all plastic. Total fire risk. The variac looked good in the pictures, and in person it didn't look much worse. A couple of minor dents in the case, easily fixed. The fuse was blown, so I put in a new one, 25A, and tried to power it up again, but nothing except it blew that fuse instantly. Hmm.

Took it apart and come to find out the switch box was a messy hack job, poor connections and something had obviously shorted to ground because what else makes that kind of black burn spot with ablated silvery metal in the middle? The switch was only rate 8A, that's funny. The neon does work, so that's something I guess. And internally, the variac itself looked as good as the other one, no evidence of heat or abuse, couldn't find anything wrong with it.

I cleaned the dust out and put it back together, wired a 14 AWG cord to it in a mickeymouse temporary setup, and put power to it... sure enough, nice smooth transformer sounds. It does hum more noticeably than the other (which is almost silent) but otherwise it's solid. Despite the shitty switch box, still a great buy for the price and after fixing those dents it's like new. It also has a little brass disk with "2159" stamped on it, inventory tag I guess.

I ended up leaving the seller positive feedback because the variac is actually in excellent shape, and just noted that the switch box needs rewired but that it was still a good buy for the price. I really couldn't care less about the box, I can make another one, easy.

There are the Powerstat 136B's compared to the Variac V5. The MOT is a Basler Electric BE 18052 001 from an old Frigidaire or similar, old enough to be made in the USA. I keep a fan on it to help cool it off. The North Carolina 136B is on the left and the one from Canada, with what's left of the switch box, is on the right.

Attempt to photograph an arc from the MOT but my camera is really bad for that.

Better photo of an arc from the MOT. I need to get some capacitors to make it resonant, apparently that gives you even bigger arcs. I don't run the MOT much past 90 volts, it's saturating heavily by 100V, and full mains idle current is 6+ amps. Harder to find old ones like this so don't want to burn it up.

Room is cluttered and I need to get proper cords on these but will do that when budget allows. Have a steady job now so that's less of a problem. Will post more later.
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