|[AMRadio] AMRadio Digest, Vol 69, Issue 4|
k4kyv at charter.net
Sun Oct 4 17:36:04 EDT 2009
> You can expect somewhat higher voltage from the new stack than the
> original tube rectifier - if that is a problem for the rig, then add a
> series power resistor to simulate the internal voltage drop of the
> earlier tube. So far I've only needed to do that once when the new
> higher B+ exceeded the rating of the by-pass caps in the other sections
> of the rig. Otherwise the rigs seemed to thrive on the higher voltage.
> Steve WD8DAS
That would be true only if the original rectifiers were high vacuum tube
types. With mercury vapour or xenon gas rectifiers, the voltage drop across
each tube is about 15 volts, regardless of the current. When you are
talking about 2500 or 3000 volts total on the plate, the voltage drop across
the rectifiers is insignificant.
With solid state, the voltage drop across each diode is about 0.7 volts. So
if you have 20 1kv diodes series strung to give 20kv p.i.v., you will have
approximately the same rectifier voltage drop that you would have with a set
of MV tubes.
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