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K2 KPA100 transmit test: fail

Posted by Brian - N5BCN on May 07, 2011; 5:17am
URL: http://elecraft.85.s1.nabble.com/K2-KPA100-transmit-test-fail-tp6339548.html

Hi All,

During the course of testing my recently built KPA100, I'm experiencing odd results on the cw transmit tests.  All tests, resistance, and voltage checks up until this point have been normal.

When transmitting cw into a 100 watt dummy load, things appear normal when transmitting in QRP mode (below 11 watts).  The strength of the cw signal on a separate receiver increases in strength as does the current draw up until the 11 watt level.

When the K2 Power level hits 11 watts, the high power relay clicks but the signal strength actually drops.  At 20 watts, the signal strength on the separate receiver is quieter than at 10 watts.  However, the current steadily increases and did not drop after the high power relay kicked in.

My approx current draw measurements at key down for various power levels (measured by my power supply's meter):

5 W    ~ 2 A
10 W  ~ 3 A
15 W  ~ 7 A
25 W  ~ 8 A
50 W  ~ 11 A
100 W ~16-17 A

My current draw during tune at less than 11 W is 343 mA (I have a number of option modules, fixed audio output mod, and Z10000 output buffer).

My current draw during tune at 11 W plus the fan on low is 545 mA.

I set the bias current so the current draw during tune at 11 W plus fan on low is about 950 mA, although it rises pretty quickly to above 1000 mA during tune.

As always, many thanks for your thoughts and suggestions.

73

N5BCN - Brian