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Old April 13th 04, 02:57 AM
 
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Bill Turner wrote:

On Sun, 11 Apr 2004 05:25:02 GMT, wrote:

I'd use
2 51K 2 watt resistors in series across each cap, to
give a very good safety margin on the resistors' power
dissipation and voltage exposure.


__________________________________________________ _______

Also, avoid carbon composition resistors. They are notorious for
gradually changing their resistance over time. Metal oxide film (MOF)
types are much more stable over the long run. Richard, AG6K, sells them
pretty reasonable. See
http://www.somis.org/

Richard's resistors are 100K and are rated at three watts. With 416
volts applied per your example, they dissipate 1.7 watts, which should
be a sufficient safety factor. The truly paranoid may connect four of
them in a series-parallel arrangement across each capacitor.

--
Bill, W6WRT
QSLs via LoTW


Thanks! Those are good resistors - I didn't know
about the site. My paranoia extends to the caps, too.
I would use 7, myself, yielding a total of 3500 volts
or about 360 across each cap and resistor. That would
also reduce the power the resistors would dissipate to
about 1.3 watts, but the reduction in cap voltage
is more important. The last one I built (for 1800V)
used 6 450 volt caps and 12 51K 2w resistors. Wish
I had known about that site when I built it - I would
have used those resistors.