[Amps] Variac repairs

[K1SG at aol.com]

In pre-testing a junkbox Variac before using it for filament control, I  
watched it arc and spark and burn out the winding near the high voltage  end.  
Does anyone do Variac repair and rewinding? Or is that another "lost  art?"
As a side question, I was running the variac into a step-up transformer,  
which was unloaded. Does the primary of an unloaded transformer present a  
significant load? Some Specifics: 5A Variac driving a 120:240VAC transformer 
of  unknown power capability, weighing probably about 10 pounds. I know if I 
put a  2.5 A load on the 240V side, I'm drawing 5A through the primary, so 
I'm staying  well below that level. The question is, do winding resistance, 
core losses, etc,  add a large enough load to fry the Variac in front of the 
transformer?
Thanks,
 
Steve
 
Steve  Gilbert
K1SG
K1SG at AOL.com
508-435-9133
FN42fe