[Elecraft] Bug in K2 PC command firmware?

[Jack Smith]

In trying to run some automated tests on my K2, I'm running into odd 
results with the PC command

The K2 is equipped with the KPA100 amplifier and I'm running the serial 
command in K20 mode.

What happens is that if the front panel power control potentiometer is 
set at 10 watts or below, PCxxx commands are properly interpreted by the 
K2 where the power command is for 10 watts or less. The echo back is 
correct and applying higher than normal audio input signals confirms 
that the power control / ALC is properly functioning.

For example:
1. Set front panel control for 10.0 watts
2. Send PC001; followed by PC; and the K2 reports 001 watts.
3. Apply audio  tone at 1 KHz to microphone input and ALC limits the 
power to around 2 watts with gross over-drive.

This is OK.

Now without adjusting the front panel power potentiometer, send the 
following:
1. PC020; which should command 20 watts.
2. Send PC; to echo back the power level. Instead of returning PC020; 
the return is PC015; Likewise if PC040; is sent, the return is PC015;
3. Apply varying audio tones and in fact the power maximum indicates the 
K2 is limiting to 15 watts nominal (I can see around 18W with gross 
overdrive in this condition.)

This is not OK.

Now adjust the front panel power potentiometer to 100W.
1. Send PC001; and then query the K2 with PC;. The response is PC001; 
which indicates  the power level is set for 1 watt.
2. Apply audio tone and adjust while watching power. The actual maximum 
power output is around 8.5 watts. The same is true for any PC power 
command up to 15 watts.

This is not OK.

What seems to be going on is that the firmware mishandles power commands 
depending on the front panel power potentiometer setting.

This had me chasing my tail looking for problems in the KSB2 board, in 
my test equipment and in my control software. It seems that those are 
all correct but the problem is how the front panel power control 
potentiometer and PC commands interact.  If it's a hardware problem in 
my K2, then the PC015; response to a PC040; command would occur.

Can anyone confirm this is a K2 firmware problem?

Jack K8ZOA