[Elecraft] KPA500: birdies on 6m from LCD backlight

[Bob]

I have an older KPA500.  I just scanned the entire 6 meter band and
couldn't find the birdies you were referring to.  I tried all the
brightness levels for the LCD and never noticed anything either on the P3
or in the K3.

That made me think of a problem I was having with my P3 a long time ago.
The coax that shipped with the unit (interconnection between the K3 and P3)
was defective and was letting all sorts of signals into the P3.  I replaced
that with a high quality coax cable and the issue went away.

Is it possible that might by the problem?

73, Bob, WB4SON