[Elecraft] KPA500 Transformer

[Bert]

Agree 100%!!!
Bert VE3NR

On 2020-10-20 8:11, jimn4kh wrote:
> I wasn't my intention to resurrect an old thread. I checked the 
> archives before posting my message yesterday. I found a little info 
> but not much. Perhaps I missed it. I delayed going to the list but 
> Elecraft tech support is apparently really backed up because I've 
> gotten zero response to my emails and voicemails beyond one email with 
> the hum mitigation tech note I mentioned before. I thought perhaps the 
> larger community had a specific solution. Judging from the widely 
> varied responses I've gotten ovciously not. I've tightened, loosened, 
> and moved the transformer around multiple times with no change. I'll 
> go get a torque wrench and try that but I cant imagine it resolving 
> the problem given how loud it is. Ill take it all apart first and try 
> the procedure once and see if it helps. I just dont like having to 
> solve problems through expermention on a $2k+ amplifier.
> Jim N4KH
>
>
> Sent from my Verizon, Samsung Galaxy smartphone
>
>
> -------- Original message --------
> From: Eric Norris <norrislawfirm2 at gmail.com>
> Date: 10/19/20 11:37 PM (GMT-06:00)
> To: Bert <ve3nr at bell.net>
> Cc: "elecraft at mailman qth. net" <elecraft at mailman.qth.net>
> Subject: Re: [Elecraft] KPA500 Transformer
>
> The torque spec is called out in the manual.  Why not use a torque wrench?
> Can we please not resurrect the KPA500 hum thread already beat to death
> multiple times years ago?  Or does everyone need to chime in yet again?
>
> 55 inch-pounds.
>
> 73 Eric WD6DBM
>
> On Mon, Oct 19, 2020, 9:15 PM Bert <ve3nr at bell.net> wrote:
>
> > Toroidal transformers cause very little acoustic hum, unless the core
> > is not tightly wound or the copper wire windings are loose!
> >
> > If you have to tighten the mounting bolt with a torque wrench
> > to get the transformer quiet, something is wrong!
> >
> > Bert VE3NR
> >
> >
> >
> >
> > On 2020-10-19 19:59, Jim Spikes N4KH 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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