[Elecraft] K3S/100 very low TX power

[Ian White]

My K3S/100 has gone into an unusual state where the maximum power
available - on any mode, any band - is about 1.5-2W. This is independent
of any PWR setting above 1W, and the PA does not engage at higher PWR
settings.

All this began on Friday afternoon when I switched on the rig. The K3S
had been working normally a few weeks ago, but hadn't been used for
transmitting in the meantime.

An external power meter confirmed that the TX could not deliver more
than about  1.5-2W. This was  confirmed again by the failure messages
from a TX power calibration. While troubleshooting, I progressively
uninstalled the KPA3 followed by the KPAIO3A adapter board, but with no
change. Even in the simplest 10W configuration with only the small
bridge board in place between the two PA connectors, the K3S would still
only deliver 1.5-2W with no effective PWR control.

I also tried most of the other common tests: unplugged everything else;
reloaded an older saved configuration; EEINIT; reloaded the saved
configuration again. No change.

But I also noticed that the firmware was one release behind the times,
so for lack of any other ideas I did a complete firmware upgrade to the
latest MCU 5.35 / DSP 2.86 / FPF 1.24 - and it started working again!
Normal power output up to 10W, and fully variable up to 100W after
reinstalling the PA module. Another TX calibration confirmed that
everything was fine. 

That pleasant surprise seemed to indicate that the problem had been more
related to firmware than to hardware.

By Friday evening, I believed the problem had gone away... but I should
have known better. 

Today it has failed again, exactly the same way as before. Reloading the
same latest firmware didn't work a second time.

So now it's the weekend and I'm all out of ideas.

While I wait until Monday to contact Elecraft Support, could anyone in
the group offer any suggestions, please?


73 from Ian GM3SEK