[Amps] Variac repairs

[texasrf at aol.com]

Steve, I have seen that smoking variac problem a couple of times and both  
times were due to my wiring error.
 
If you somehow connect 120vac between the wiper and one end of  the 
winding, as you rotate the shaft the 120vac gets connected to fewer and  fewer 
turns until smoke is released.
 
Others have mentioned how to repair the unit.
 
73,
Gerald K5GW
 
 
 
 
 
In a message dated 12/26/2009 3:38:23 P.M. Central Standard Time,  
K1SG at aol.com writes:

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
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