[Elecraft] K3 Power Amp Shut Down Problem

[Don Nelson]

Hi all,

My K3 appears to be working just fine once the power amp shut down problem
was fixed. For months after I had assembled the K3, I would occasionally to
frequently experience power amp shut down failures. The power amp shut down
failures would occur while transmitting. The power amp shut down would occur
sometime after I had been transmitting for a while and sometimes when I has
been transmitting only for a very short time. This problem appeared to occur
mostly on the 10m band.

The problem appears to have been an intermittent BNC connector on the coax
cable that I was using. This cable worked fine on other radios but not the
K3. When I changed the cable to the K3, the power amp shut down problem went
away. I have been trouble free for about 6 weeks now.

Lessons learned: (a) use good cables with good connectors, (b) be aware that
the K3 has hair trigger protection logic that shuts down the PA, (c.) the K3
needs to have messages displayed on the front panel when it decides to shut
down the power amp giving a cause for that action, (d) the K3 documentation
needs to enumerate the actions the firmware may take to change the state of
the radio, in particular when the PA power is shut down.

Had I been able to read about the protection logic built into the firmware
to protect the power amplifier, I would have saved months of frustration
trying to figure out what was going on. It would be greatly appreciated by
me and surely many others if the user manual would discuss the protection
logic in the firmware and where and when power down actions will be taken.

Had the firmware reported protective action taken to shut down the power
amp, this too would have hastened my taking corrective action. It would be
so easy for the firmware to display, say on the VFOB display, that high SWR
caused the power amp to be shut down.

Don Nelson, N0YE

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