What might work if it's shorted is to clean the dust off and spray it with some Dielectric Epoxy paint. It's thin enough to seep into the windings and seal any bare spots.
I fixed the HV transformer in a Raytheon this way. It wasn't really shorted though, just arcing internally somewhere.
Ignore the price on this link, that's for a case of the stuff, it's about $8 a can locally.
http://www.uneedit.com/industrial-eq...oating-205-403