[Elecraft] Ameritron 240V inrush limiter: any benefit on a KPA500?

[Edward R Cole]

I used on-rush current limiting series resistors on the 240vac input 
to my 4200 volt transformer and one on the 5v filament of my 8877 
amplifier.  The filament drew normal 11A, so on-rush was 
huge.  Simple resistor-capacitor time constant timer controlled relay 
to short out large 50w and 100w  current-limiting resistors.  Relays 
were 12vdc so a diode rectified the 240vac and I supplied 12v to the 
filament relay ckt from amplifier control panel.

I also had a 100-ohm current limiting resistor on the 4200v PS output 
to protect from HV arc over's.  G3SEK Triode Board was used for bias 
and amplifier over current protection; It provided 5-minute warm-up 
delay for HV to the 8877.

I've retained my 8877 project web-page for information, though it was 
sold in 2018.  Now run only sspa's:  KXPA100, 1000w Harris on 6m, 
1500w W6PQL sspa on 2m, and 600w sspa on 1296.  No more "bangs" when 
HV goes to ground.  SSPA's all use 50v-50A switching PS.

73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   dubususa at gmail.com