[Elecraft] KX3 TX calibration failure on 52 MHz

[Tuck Watkins]

The problem is the KX3 TX calibration is failing on 52 MHz at 4.0 W. I
would appreciate some advice on how to proceed with diagnosis and
correction.

First the basic background information: KX3 #8094. Firmware versions:
MCU = 2.33, MCU = 1.33. I'm running the KX3 configuration utility Ver.
1.14.4.11 on Linux Mint 17.2
[uname -a => 3.16.0-38-generic #52~14.04.1-Ubuntu SMP Fri May 8 09:43:57
UTC 2015 x86_64 x86_64 x86_64 GNU/Linux ].

To calibrate I did the following:

I attached a suitable 100W dummy load to the KX3. Then I ran the KX3
configuration utility. I executed the TX Calibration Gain. It runs fine
with no errors until it reaches 52 MHz. The relevant lines with the
failure message on the computer screen are:

    Calibrating 52.000 MHz
    TxGainStartTune Invalid response to "TQ;"
    Calibration failed

I then decided to try the TX calibration instructions in the KX3 manual.
As with the KX3 utility all went well except for the 4.0 W at 52 MHz
test. When I got to 4.0 W on 52 MHz it appeared that the output was
stable. That is the 4.0 W was holding steady. When I pressed the button
to turn off the tuning the message in VFO A displayed was "d=017." The
message in VFO B was "ERR TXG." I repeated the test at 4.0 W. The
message in VFO B stayed the same. The message in VFO A changed to
"d=042." A third attempt produced "d=046" message in VFO A. VFO B had
the same "ERR TXG" message.

I then ran the test at 6.0 W. There was no error. The error does not
suggest what to do next. Any advice would be appreciated.

Thanks all,

Tuck, W6TUK