[sdiy] Tube amp cap discharge tool?

[Harry Bissell Jr]

Almost all tube amps have bleeder resistors
because of using two electrolytic caps in
series to get the voltage rating.  Its possible that
some small wattage units DON'T... so be careful.

The bleeder resistors serve to balance the charge
equally in the series connected caps.

If there ARE bleeder resistors, dielectric absorption
cannot re-charge the caps (unless you remove the
bleeders)

H^) harry

--- René Schmitz <uzs159 at uni-bonn.de> wrote:
> 
> Hi Michael,
> 
> > Can anyone give me a quick recipe for a safe tube
> amp capacitor discharging 
> > tool?  That is, something I can use to discharge
> the voltages found on filter 
> > caps in tube amps after you turn the amp off, so
> it will be safe to stick my 
> > hands and tools in there to work on them.  I'm
> guessing that I need something 
> > like a fairly large value, high wattage resistor
> connected on one end to a test 
> > clip that I hook onto chassis ground, using the
> other end of the resistor to 
> > touch the hot side of the charged-up capacitors to
> shunt the charge to ground, 
> > but I'd like to know for sure if this is the right
> way to do it, and if so, 
> > what value should I use for the resistor (both
> resistance and wattage).  Any 
> > other tips about precautions, procedure, or
> techniques would be much appreciated. 
> >  Sorry to be such a pussy about this, but for some
> odd reason, I am not so 
> > much in the mood for electrocuting myself today.
> 
> 
> Best thing is to put bleeder resistors across the
> caps *permanently*. 
> Say 33-100k or so, power handling depending on the
> voltage P=U²/R. Then 
> you can always work safely after a couple of minutes
> (tau=R*C, takes 
> several tau's until the voltage is safe though). The
> thing is that high 
> voltage caps can charge them selves up again, due to
> dielectric absorption.
> 
> Cheers,
>   René
> 
> -- 
> uzs159 at uni-bonn.de
> http://www.uni-bonn.de/~uzs159
> 
> 
>