[Elecraft] KPA 500

[Bob McGraw K4TAX]

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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