[Elecraft] KPA500 Transformer

[Eric Norris]

When the KPA500 first came out, there were lots of complaints about hum.
This made it difficult for Elecraft Support to differentiate between normal
hum, which I can barely hear, to the obnoxiously loud hum of a misaligned
transformer.  I finally called support so they could hear the hum of my
KPA500, which was in the obnoxious category.

Take a breath, you can fix this.  Tweaking the bolt torque, and slightly
moving the transformer, requires only removing the cover.  If you don't own
and can't borrow a torque wrench, given your investment--buy one.  A small,
inexpensive one will do the trick as the torque is quite low.

73 Eric WD6DBM

On Mon, Oct 19, 2020, 5:00 PM Jim Spikes N4KH <jimn4kh at gmail.com> wrote:

> Looking for details from anyone who resolved issues with excessive
> transformer hum during transmit on a KPA-500.
>
>
>
> I have a hum mitigation application note sent from Elecraft tech support.
> But the procedure recommended is pretty involved - removing front/side
> panels, un-plugging connections, removing the transformer, changing
> positions of the rubber discs, and putting it back together. Possibly more
> than once, depending on the results.
>
>
>
> There is a risk of breaking something, and I'm not sure its going to solve
> the problem if I'm successful. This is a new out of the box KPA500 kit.
>
>
>
> If anybody has any lessons learned I would appreciate hearing them.
>
>
>
> Jim, N4KH
>
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