[Elecraft] KPA500: Reduced HV sag by 9V by using 240V feed

[Fred Townsend]

Bob, did you make any temperature measurements? I bet the amp ran cooler
too.
73, Fred, AE6QL

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bob
Sent: Saturday, July 21, 2012 12:31 PM
To: Elecraft at mailman.qth.net
Subject: [Elecraft] KPA500: Reduced HV sag by 9V by using 240V feed

When I purchased my KPA500 at the end of last year, I didn't have a 240V
outlet in the ham shack, so I as forced to run off of a 120 volt line.  In
addition the ham shack is about 75 feet away from the breaker box, so there
was some pretty hefty IR drop on the 12AWG cable.

When I was running 118 Volt AC input the KPA500 had the following readings
on 20 meters:

Standby:  HV 75.9 V
500W Out:  HV 54.5 V at 14.5 A
K3 Drive:  36 Watts to produce full Output

I finally ran a 20 Amp 240 circuit into the ham shack today.  With 237 Volts
AC input to the KPA500, I now see the following:

Standby:  HV 77.6 V
500W Out:  HV 63.5 V at 14.5 A
K3 Drive:  34 Watts to produce full Output

Not that this will be a surprise to anyone that the amp should be run off of
240 volts if possible, but it is interesting to note that by doing so the HV
sag at 500 watts output has been reduced by 9.0 volts.

73, Bob, WB4SON