[Elecraft] KPA500 clicking

[Wes (N7WS)]

Bob,

Thanks for your answer.

Hopefully, it lays to rest the idea that I didn't know what I was talking about 
when I described it as the sound of a reed relay following the key.
  (Hmm, mechanical motion initiated by electromotive force....sort of describes 
a relay doesn't it?)

That said, I'm not sure the phenomenon is totally due to magnetostriction. 
"Coil Noise" may be a better explanation. (http://en.wikipedia.org/wiki/Coil_noise)

In the case at hand, I'm a bit concerned about having this happen.  Perhaps it's 
from spending too many years around a failure analysis lab or doing vibration 
testing on assemblies, where with a strobe light we could watch things move to 
the point of failure.

What is Elecraft's fix?

Wes


  On 12/30/2014 12:29 AM, Robert Friess wrote:
> What you are hearing is due to magnetostrictive force causing the windings
> of the inductors in the TR switch to bang against their cores as the TR
> switch bias is applied.  There are no relays.
>
> 73
> Bob, N6CM, KPA500 design engineer.
>
> On Mon, Dec 29, 2014 at 10:23 PM,<mcduffie at ag0n.net>  wrote:
>
>>> RF may be switched with PIN diodes, but there are some relays in there
>> someplace.
>>
>> No TR relay.  Amp is quiet as a mouse when keying/unkeying, even in QSK.
>> There
>> IS a STBY/OPER relay, I assume, as I can hear it when I go in and out of
>> OPER.
>> Also, band switching, of course.
>>
>> There are ticks due to heating in the heat sink, but not in time with
>> keying.
>> Random, and varying rate.  Documented on this group previously.
>>
>> Have you asked Elecraft (not this list) for a diagram?
>>
>> Gary
>>