[Elecraft] KPA500 Hum when off?

[Matt NQ6N]

I had this happen and discovered that the laser printer I had was plugged into the same ac circuit and was causing voltage drop periodically. Moving the printer to another wall outlet fixed the problem. 

Matt NQ6N

On 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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