[Elecraft] KPA500 Proper Transformer Tap setting

[Jim Brown]

On Sun,3/22/2015 1:20 PM, Jack Brindle wrote:
> The two sentences are not in conflict. You should expect a major drop in HV on
> key-down due to losses in the power supply. This includes the components in
> the KPA500 (transformer, etc), the power cord, plug, wall outlet and wiring all
> the way to the main pole transformer. You can’t do much about most of this,
> but making sure the power cord can handle the current without overheating is
> a great idea. Of course this problem is worse with a 120V supply than 240V
> since the current is proportionately higher.

IF the wiring between the breaker panel and the outlet is under your 
control, it is a very good move to use bigger copper for that run. #14 
is minimum for a 15A circuit, #12 for a 20A circuit, but going up to 
#`10 will reduce the IR drop under load. When doing the calcs, remember 
that the line current is NOT a sine wave, but rather pulses centered 
around the peaks of the waveform to recharge the input filter caps. That 
means that the voltage drop will be greater than if it were a sine wave.

I have 240VAC in the shack to run my big tube amps, so I also run my 
KPA500 from 240V.

73, Jim K9YC