New Variac for Joule Electra Amps

Hi Jea48,
Thanks for the input. The variac is the latter; manually 'dialed up' to operating voltage of approximately 166 volts. It's not a branded variac; it came with the amps, and am sure is designed for the amps. It's part of how the joule amps work. Even the latest Joule amps have a variac, but they are internal, one per amp, but mine is a single, outboard one. It's not an optional piece of kit - my amps won't function without it.

The reason I need a new (or rebuilt) one is because it's no longer working properly; the core has likely failed, because it's sparking a bit when I initially dial it up, and then glowing, with a slight burning smell when operating.

I have a VZN-80. It is 7 years old. Last year, the variac started to get very hot and there was a burning smell. I did not look to see if there was any glowing. I took the variac to my local tech, and it turned out the problem was a defective fuse holder. He said the one provided by Joule was under-spec'd. He put in a higher value fuse holder, and all has been well since.

Outlier,

Sounds like you slowly ramp up the variac with the amps connected, powered on, and then set the desired voltage under load. This action over time will cause wear on the brush that contacts the autotransformer winding directly proportional to the connected load of the Joule Electra amps.

First I would not try to use the variac until you have it checked out. It could be something as simple as a fuse holder as Thaluza stated in his post. Or maybe even a loose connection. Or it could be more serious like a bad brush on the dial slider arm that contacts the winding of the autotransformer. If that is the case hopefully the autotransformer winding is not damaged.

If you are the least bit mechanically inclined you could pull the cover from the variac and have a look inside.... Make sure the variac is unplugged from the mains AC power before you start.... You could then see where the problem is. Look for a burned spot that will more than likely show signs of black carbon and will have a burnt smell.

Here is a nice video I found doing a Google search.

https://www.youtube.com/watch?v=M8cJrJyR87o
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Jim

Thanks guys for the input. I'm not so mechanically inclined, but am ambitious enough to try.

The variac used to have the original (small) fuse holder scenario, and the fuse kept failing on me, so I sent it back to Joule and they replaced it with a massive essentially external (sticking out) fuse assembly which has since been bullet proof, so I don't think it's the fuse in this case. Just to be sure, I had swapped out a new fuse just to see if there was any change in operation and the sparking, glowing and burning symptoms were still there.

I'll see if I can investigate further

I managed to open the variac and I saw that the windings were blackened generally, there was little to any 'brush' to speak of and probably most worrying, there was a vertical segment of the winding that was essentially gone (the outer metal winding was likely smoke/carbon at this point, revealing an inner winding. I guess it's hard to describe but I have the photo.

I wish I could just buy a cheap new one or have this one fixed quickly, but am guessing there's no recourse there?

I guess I'll have to bite the bullet and ship it to the after-warranty service dept.