[Amps] Henry 3kA Choke input Pwr Supply Overvoltage Query

[TexasRF@aol.com]

Choke input filter type power supplies require a quite a bit of bleeder  
current to prevent voltage soaring like you describe. You can find more  
information about this in your handbook. I suggest you confirm that the bleeder  
resistor(s) are in good condition.
 
73/k5gw
 
In a message dated 11/18/2005 8:23:58 A.M. Central Standard Time,  
w2cqm at juno.com writes:

Since  I'm relatively unfamiliar with the characteristics of a vintage 
Henry 3KA  choke input power supply, perhaps someone would comment on a
question that  has arisen regarding what appears to be  too high an  output
plate  voltage. The Henry is equipped with a 10Hy fixed choke  tuned with
a .1mFd @ 7500VDC capacitor. The diode configuration is full  wave bridge
with the choke wired in series and situated before the filter  capacitor;
for a typical choke input circuit. All components are OEM  Henry.  A Plate
transformer output is 3300VAC with a nominal   input rating of 230VAC.
There's a 4  terminal manual step start power  up switch (position 1-off),
voltage fed through resistance wire in  position 2 for the soft start, 
a  CW tap (position 3 which shorts out  the resistance), and a  third SSB
tap, position 4.  In the no  load  CW position, DC voltage is over 4KV and
in the SSB (higher tap)  position the plate voltage is close to 5KV. 
Henry only provides a   full scale plate meter calibrated for 4KV so the
dial deflection  obviously   is off scale. These high voltage values are
verified  independently  with a calibrated  Triplett  meter. In  addition,
they appear to be significantly  higher than  the  levels suggested in the
operator's manual.  Tested the choke for  resistance (about 56 ohms) and
the tuning capacitor is not shorted. My  primary voltage is somewhat
higher (248VAC) so that may account for some of  the overvoltage. However,
to my mind, the resulting operating voltage is at  least 800-900VDC too
high and of course is causing some concern. I've  verified that the wiring
is correct and I'm asking for any comments that  may explain the higher
levels of plate voltage. Any comments would be  appreciated. Ron  W2CQM/3
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