Hi Scott,
We have seen this in rare cases on a few 1500s. It appears to be caused by the
ground connection between the rear RF INPUT SO-239 flange and the chassis.
Very slightly loosening (not too far!) and then firmly re-tightening all four
screws on this SO-239 connector will insure a good ground connection between
this connector and the rear panel. (There are lock washers between the nuts and
the SO-239 inside.)
If the screws are loosened too far, you may have to remove the bottom cover of
the amp to hold the interior nuts in place while you re-tighten the four
screws. (Make sure the 50V power and control cables are disconnected when you
remove any covers on the amp.)
73,
Eric
/elecraft.com/
On 12/14/2019 1:43 PM, K9MA wrote:
I guess it just shows how little I've been on 10, but I've had the KPA1500 for
over a year now, and I just noticed that when I turn it on, my noise floor on
10 goes up about 3 dB. (And that's from an urban noise floor.) It's pretty
flat over much of the band, not typical switching supply noise. Has anyone
else experienced this and found a cure? (Other than using the old amp tube.)
73,
Scott K9MA
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