[Elecraft] KPA500 Hum when off?

[Jim Miller]

Hi Eric

It isn't a continuous hum, nor does it sound like a small transformer. It
comes on for perhaps 15 seconds, sometimes more, then goes away. Nothing
shows on the front panel when this happens as it is "off" but back panel
switch is on. It sounds more like a big transformer hum.

I've got a line voltage monitor setup now and I'll try to correlate any hum
with line fluctuations.

Thanks

jim ab3cv


On Tue, Jun 11, 2013 at 5:03 PM, Eric Swartz - WA6HHQ, Elecraft <
eric at elecraft.com> wrote:

> This is normal and is due to the small low voltage transformer and
> rectifiers that provide power to the front panel microprocessor. turning
> off the rear switch will turn everything off, including this transformer.
>
> Eric
> elecraft.com
>
> On 6/11/2013 10:13 AM, Stan AE7UT wrote:
>
>> I have a kit-built KPA500 that has the same issue.
>> It's well grounded and all the bolts are tight.
>> The humm is barely noticeable when off but definitely there.
>>
>> 73
>> Stan AE7UT
>>
>>
>>
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