[Elecraft] KPA-500 Buzzing noise

[Dave Gynn]

First of all I¹m new to this forum having just taken delivery of a KPA-500
and KAT-500 pre built by the Distributors in the UK.

What has surprised me is that when either tuning or operating the KPA-500
with WSJT-X  there is a very noticeable buzzing noise, not a transformer
hum, from the unit. The Power output LED¹s light up but the last one appears
to flicker at the same frequency as the buzzing.. This happens irrespective
of whether the output is 50w or 300w. The KPA-500 is driven by a Flex-6700.

Grateful to know if anyone else experiences this?  I was expecting a very
quiet unit but this buzzing is quite disconcerting.

Dave
G3SBP