[Elecraft] KPA500 Noise While Off

[hawley, charles j jr]

Triac switch would do it. Seems like a natural for equipment but seldom used.

Chuck Jack 
KE9UW

Sent from my iPhone, cjack 

> On Jun 27, 2018, at 2:54 PM, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
> 
> Yes that is the magnetization current of the transformer core. 
> Doesn't happen when powered up at the zero voltage crossing point. 
> 
> One person advised to always turn on equipment at the zero crossing point.  Seems like a good idea.  Now if I could only get my finger timed correctly to do this. 
> 
> Bob, K4TAX
> 
> 
> Sent from my iPhone
> 
>> On Jun 27, 2018, at 2:42 PM, hawley, charles j jr <c-hawley at illinois.edu> wrote:
>> 
>> I’ve only noticed a thump with a piece of equipment which has a power supply when it turns on at a line voltage peak. On the occasion that it turns on at a line voltage zero crossing, it makes no noise at all.
>> 
>> Chuck 
>> KE9UW
>> 
>> Sent from my iPhone, cjack 
>> 
>>> On Jun 27, 2018, at 2:10 PM, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
>>> 
>>> Seems that the AC line supplying the equipment has a rather high impedance thus allowing the voltage to suddenly drop under the dynamic load and then surge to a higher than normal value. 
>>> 
>>> A dedicated 120V and/or 240V service should be considered for the station power. 
>>> 
>>> Laser printers do draw considerable power when they start. 
>>> 
>>> Bob, K4TAX
>>> 
>>> 
>>> Sent from my iPhone
>>> 
>>>> On Jun 27, 2018, at 2:00 PM, John Simmons <jasimmons at pinewooddata.com> wrote:
>>>> 
>>>> My Astron RS35 does the same thing under the same conditions.
>>>> 
>>>> -John NI0K
>>>> 
>>>> Matt NQ6N wrote on 6/27/2018 1:20 PM:
>>>>> My KPA500 makes a noticeable hum/thump when the laser printer that is on
>>>>> the same circuit draws a lot of current.
>>>>> 
>>>>> 73,
>>>>> Matt NQ6N
>>>>> 
>>>>> On Wed, Jun 27, 2018 at 12:58 PM Jim Brown <jim at audiosystemsgroup.com>
>>>>> wrote:
>>>>> 
>>>>>>> On 6/27/2018 10:37 AM, Richard Wade wrote:
>>>>>>> If I had to venture a guess, I would say that somehow the unpowered
>>>>>> KPA500
>>>>>>> was picking up noise on the shack wiring.  Very strange. Is that
>>>>>> possible??
>>>>>> 
>>>>>> It is if equipment in your shack is not properly bonded together, and to
>>>>>> house grounds that are also properly bonded together. Study N0AX's
>>>>>> recent ARRL book on the topic, to which I contributed, or the slides for
>>>>>> a tutorial talk I've done at several hamfests.
>>>>>> 
>>>>>> http://k9yc.com/GroundingAndAudio.pdf
>>>>>> 
>>>>>> 73, Jim K9YC
>>>>>> 
>>>>>> 
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