Folks,
John was quite correct to term his test an 'Endurance Test'. I have
worked as an Assurrance Engineer for the latter part of my career and
would like to offer the following:
The purpose of any 'burn-in' tests for complete electronic assemblies I
have encountered is *not* to stress the DUT to its limits, but simply to
catch any early life failures that may be lurking. Burn-in testing of
individual devices is different than any burn-in of a complete
assembly. Simply running the assembly continuously under normal
conditions for a period of time is normally sufficient.
Early life failures can and do occur, but they are not common.
If one would want to do a 'burn-in' for the K3, I would advocate that
alternate receive and transmit cycles be done over a period of a
several days (half max power level should be sufficient) or so (you get
to pick the time frame that *you* define as 'early life').
Other than catching early life failures, a burn-in period for electronic
packages such as the K3 serve no purpose at all. The continuous
operation just makes a lurking early failure happen sooner than it would
normally. If you are expecting anything more from such a test, it just
"ain't gonna happen".
Of course, one can always just operate it as normal for the first 30 to
90 days and regard any failure that occurs as an early life failure -
that works just as well as continuous operation.
We did hear of one K3 that failed during Field Day, but there are over
1000 K3s out there, and an early life failure rate of less than 0.1% is
very good, even though it is quite disconcerting to find oneself in that
small percentage region.
73,
Don W3FPR
John King wrote:
Disclaimer - the following test method is not approved or
sanctioned by Elecraft. Conduct any testing at your own risk.
I work in Quality Assurance in my day job (30 years and counting.)
Long before FD I performed a 24 hour endurance test on my K3
to approximate worst-case FD conditions. I recorded a CQ FD message
similar to the actual message we would be using at FD into one of
the K3's message memories, then set the message repeat time to
minimum. The K3's output power was set to 120 Watts and the rig
was connected to a 50 ohm dummy load with a Bird thruline wattmeter
in line. The DC input voltage was set to 13.5 volts. The test was
performed at ambient room temp, about 24 degrees C. The K3 sent
the continuous message loop for a 24 hour period without incident.
The actual environmental conditions at our FD were a bit more
severe than the test conditions above. The K3 was operated in a
4-man dome tent exposed to full sun with an outside air temp
approaching 90 degrees. We didn't measure the actual temperature
inside the tent, but my informal assessment was "hot as hell."
Of course, the transmit duty cycle in actual FD use was less
demanding than the test duty cycle. I had high confidence that
the K3 would be up to the task, and it was.
I'm sorry to hear about your failure at FD. I have heard no other
reports of FD failures, and to my knowledge the VP6DX crew had
no failures during their operation earlier this year. It may be
of small comfort to you, but I regard your failure as an anomaly
- stuff happens. Overall, the K3 is establishing a reputation as
a very reliable field rig.
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