[Elecraft] Exaggerated K2/100 Current Readings

Todd Fonstad [email protected]
Sun Feb 16 23:05:00 2003


Greetings,

My K2/100 (with the KAT100) is apparently giving exaggerated current
readings on its LCD display. On 40 meters, for example, the display shows
11.9 V @ 21.4 A with 100 watts output into a dummy load. The voltage seems
to be low by a volt or more, as I was using a 13.6 V power supply for this
test. I read the voltage across the current-sensing resistor R7 on the
KPA100 board as 54.2 millivolts. According to the manual (p. 48), dividing
this by 5 gives the Q1 and Q2 collector current as 10.84 amperes. It would
seem that the total consumption of the unit at 100 watts out should be in
the neighborhood of 12 A, not 21.4 A. Some bands show even greater current
readings: 27.2A on 20 meters and 28.4 A on 17 meters.

I normally use the MFJ 25 Amp "MightyLite" switching supply. It has no volt
or amp meters. However, it is fitted with a 20 amp fuse in the output, and
that has never blown despite the higher indicated readings on the K2.

The problem seems to occur only when the K2 is in the "high power" range. At
ten watts out (low range), the display reads 12.6V @ 2.60A. At eleven watts
out (high range), the display indicates 12.6V @ 10.4A. That the output
increased by only one watt was verified by my Autek WM-1 Computing Meter.

Do any of you have a clue where I made a cold solder connection on the KPA
board <g>?

72/73
Todd
N9NE