[Elecraft] KPA500 Transformer

[Macy monkeys]

Even the 'normal' hum was too much my tastes. My KPA500 is now on the floor, under the desk with a remote digital readout on the desk. 

John K7FD

> On Oct 19, 2020, at 6:25 PM, Eric Norris <norrislawfirm2 at gmail.com> wrote:
> 
> 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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