Residual charge left on caps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

While the power supply transformer will rapidly discharge a single tank cap 
in a normal configuration, there are circumstances that still warrant a 
bleeder resistor.  I once attempted to determine the best primary tap point 
on a live system, using an insulated pole to drag the primary tap across 
the primary turns.  The arcing between the tap wire and the primary turns 
was predictably scary and I quickly abandoned that idea.  I turned off 
power, and picking up the tap wire, I placed it onto the primary, and ZAP, 
a VERY a very painful discharge through my hand.  Luckily no vital organs 
were involved, or perhaps the cap was less than fully charged.  Point is, 
the power supply can't discharge the cap if the circuit is not complete.

On why MMC caps develop asymmetrical charges, and that it may be due to 
corona, I've also seen my 4-element cap powered by a 4kV NST, develop 
residual charges before I installed bleeder resistors.  I would have 
guessed that 4kV would not generate that much corona, but I'm not sure.

Moral of both stories is, I will always use bleeder resistors.

Gary Lau
MA, USA