My first question is "what does it do on a dummy load?" Sounds like
something related to a bad or questionable jumper cable, loose connector
or bad connectors. I find many of today's connectors have machining
tolerance errors and more so, have only "good looking" plating. While
in fact, many of these are poor quality.
I find that PL-259 connectors must be mated correctly in that the body
of the connector has 2 small triangle shaped protrusions from the body
of the connector that must be mated with the notches on the SO-239
connector. Failure to do this will allow the connector to loosen under
use. And then the shell of the connector must be tightened a bit more
than finger tight. I keep a 4" pair of Channel Locks on the desk to
help remove and tighten connectors. If not done so, the heating and
cooling of the connector will allow it to loosen and not make good contact.
Regarding the KPA500 temperature: With my amp this morning { S/N 3519
Firmware 01.54 } at turn on 18C, I then held it at 500 watts carrier
output into a 50 ohm dummy load. At 50C fan on 1 speed, at 55C fan on 2
speed. This took about 210 seconds (3.5 minutes) from cold start to
55C on 80M into the dummy load. Other bands are less efficient and one
could expect a faster temperature rise in less time. It does vary from
band to band and antenna load to load. I did not observe any change in
SWR indication, either on the amp LED display or my Bird 43 between the
amp output and the dummy load.
Hope this helps.
73
Bob, K4TAX
On 4/10/2020 6:26 AM, Alan - G4GNX wrote:
I have a strange fault a couple of times recently, where the SWR
starts to increase during the time of a single 'over'. I've been using
the K3S set at 100W out, via the KPA500 (in standby) and the KAT500
tuner, without any problem, but after I've switched the linear to
Operate and driving it to 200W, the SWR creeps up. I don't think it's
an antenna issue, but a possible heat problem with the KPA500. I
watched the temperature display on the KPA500 and initially on Standby
it shows about 38 degrees C. After transmitting at 200W the
temperature slowly rises above 60 degrees C, but the fan doesn't cut
in. Does anyone know if this is normal behavior and what temperatures
I should expect to see? I have tested the fan via the Menu function
and it works as expected.
73,
Alan. G4GNX
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