On Mon, 30 Apr 2018 15:45:19 -0500, Fox's Mercantile
wrote:

don't worry about carbon tracks, if you ppur this stuff
https://www.ebay.com/itm/152789446463
over the part that's arcing, the carbon will be encapsulated.

I don't know how it's possible to arc between windings with only
117/220VAC. My guess(tm) is that there's arcing between the contact
brush and the windings caused by a layer of filth on the windings or
contact brush.

No way am I going to pay $18 for 2 oz of Q-Dope.
Q-Dope is polystyrene disolved in MEK.
http://www.gcelectronics.com/order/msds/101.pdf
Make your own from packing peanuts and MEK:
https://www.youtube.com/watch?v=ANn6hti35Zc

Maybe some anti-corona goo will provide some better arcing protection:
https://www.mgchemicals.com/products/insulating-coatings/super-corona-dope-4226
https://www.amazon.com/MG-Chemicals-Corona-Liquid-Applicator/dp/B008OA7CAE

Variac cleaning videos:
https://www.youtube.com/watch?v=5vKHOSpynM8
https://www.youtube.com/watch?v=xPdIrzw2kko
https://www.youtube.com/watch?v=Mbbght6HIxM
etc...

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558