[Elecraft] K3 buzzing on key down

[Stephen Prior]

I'm getting a fairly loud buzz, almost an arcing sound coming from the
K3/100 on key down on CW, just some bands, 15m for instance. I'm wondering
if I have a ferrite bead vibrating somewhere.  I have had the transceiver
now for some years and have never heard it before.  Has anyone else found
this?  It doesn't do it all the time so is rather difficult to pin down.
I'm getting full power out without any problem.

Thanks for any advice,

73 Stephen G4SJP