[Elecraft] KPA500 Hum when off?

[dmb at lightstream.net]

Jim,

As someone else mentioned, it is most likely due to line voltage variance.
Even though they are on different circuits, whenever my wife uses the blow
dryer, the KPA500 starts humming along. I guess that doesn't speak well
for connections somewhere between the electric company and my ac outlets,
but the issue is not with the KPA500.

73, Dale
WA8SRA


> It's not fan noise. It's definitely 60hz hum likely due to transformer for
> some reason. This was a factory assembled unit. I'll take the lid off and
> check it out the bolting. I'm currently running on a shared household
> circuit with who-knows-what connected elsewhere. The shack will get a
> dedicated 20A circuit soon.
>
> Thanks all
>
> Jim
>
>
> On Tue, Jun 11, 2013 at 11:58 AM, Jack Brindle <jackbrindle at me.com> wrote:
>
>> Jim;
>>
>> Make sure the transformer is bolted down appropriately. If it works
>> loose
>> then it will cause the hum.
>>
>> Jack Brindle, W6FB
>>
>>
>> On Jun 11, 2013, at 7:51 AM, Jim Miller <jim at jtmiller.com> wrote:
>>
>> > I leave my KPA500 back panel switch in the ON position most of the
>> time
>> and
>> > use the front panel switch to bring it to life.
>> >
>> > However in even when in the "Front panel off/Back panel on" state the
>> > KPA500 will occasionally hum for a few seconds.
>> >
>> > Is this normal? Any suggested causes to worry about?
>> >
>> > Thanks
>> >
>> > jim ab3cv
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