[Elecraft] K3 Drive Levels and the SPE 1.3K-FA

[Bob McGraw K4TAX]

With the KPA3A / 100 watt amp active, which switches in at 12 watts, the 
LPA then runs about 1 to 5 watts.  The issue I encountered was running 
the KPA3A / 100 watt amp, at the lower end of the power range being 15 
or so watts.  I encountered two failures of the KPA3A amp module.

I now stay away from that power level thus running 20 to 25 watts from 
the KPA3A.  I've been doing this since May 2018 when the last KPA3A was 
replaced.     I was also advised by another ham who experienced several 
KPA3A failures to "stay away from 15 watts". The last KPA3A is the Rev E 
model that, according to the report from Elecraft, states "Replaced 
KPA3A Rev B with the more stable KPA3A Rev E  amp".

The discussion can be confusing as the LPA runs normally up to about 12 
to watts but can be pushed to near 15 watts.  The KPA switches in the 
circuit at ~12 watts. {Listen for the relay click} General discussion 
surrounds running the LPA at 12 to 15 watts in high duty cycle modes, 
thus causing failure of the LPA.  The devices are only heat sinked to 
the bottom panel and no forced air cooling is provided for the LPA.

73

Bob, K4TAX


On 11/22/2019 7:08 AM, hawley, charles j jr wrote:
> I thought the answer was to run the KPA  by going up to 12 or 15 watts. What is the LPA running when when the power is at 12 or 15 watts? What is it running when the power is at 20 or 25 watts?
>
> Chuck Jack Hawley
> KE9UW
>
>   
>