Re: CW Noise Pedestal

Clay Autery
 

My bad....  I looked at the picture more closely in the Mod instructions....  <blush>

The cap is clearly across the B+ and GND terminals for fan #1 (left fand as you look from the rear).  Don't know how I "saw" it different...  Doh... I apologize for any confusion I may have caused.


______________________
Clay Autery, KY5G
(318) 518-1389
On 01/21/20 00:10, Rob Sherwood wrote:

My IC-781 cooling kit used 470uF from the fan B+ to ground.  I haven’t seen the Elecraft schematic.   Rob, NC0B

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Clay Autery
Sent: Monday, January 20, 2020 10:29 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] CW Noise Pedestal

 

Right...  I have just never seen a bypass connected between to + terminals...  normally you see the pos term bypassed to ground...
This one LOOKS to this uneducated hacker like it is intended to "balance" the two fan circuits... And 470 uF seems a bit large for a bypass cap anyway...  I'm used to seeing much smaller ones...  even if there are several stacked values, they usually aren't anywhere near that large a value.

73,

______________________
Clay Autery, KY5G
(318) 518-1389

On 01/20/20 14:36, W2XJ wrote:

it’s just a DC bypass across the fans. Any properly rated ‘letic will get the job done.



On Jan 20, 2020, at 1:34 PM, Clay Autery <KY5G@...> wrote:



Replying to my own post... sorry....

I don't think I will personally just throw any old 470uF 16V electrolytic capacitor in there.  I think I will dig into the schematics a bit and try to figure out for what the cap is being introduced into the circuit.
Bulk, smoothing, response?  Other?

For instance, in audio applications, folks congregate around Elna SILMIC II series electrolytics for "smoothing"purposes...
I don't pretend to know ANYTHING about this, but it is an opportunity to learn.

73,

______________________
Clay Autery, KY5G
(318) 518-1389

On 01/20/20 12:23, Clay Autery wrote:

HERE is the Introduction to the Mod Alert:

Elecraft      •      www.elecraft.com     •     831-763-4211Elecraft KPAIO3MDKT

Installation Instructions
Revision B, August 10, 2016E740287Copyright © 2016, Elecraft, Inc.All Rights Reserved

Introduction

This modification applies only to K3S transceivers equipped with the KPA3A 100 watt power amplifier, serial numbers 10732 (factory assembled), 10728 (kits) or below, and to all K3 transceivers with the KPA3 power amplifier that have been upgraded with KSYN3A synthesizers.Tests at Elecraft have shown that a very small amount of electrical noise associated with the fans on the KPA3 (or KPA3A) amplifier module can be detected in the transmitted signal under laboratory test conditions. This modification suppresses that noise. The noise had always been present, but was only discovered with the addition of the new KSYN3A synthesizer, due to its extremely low phase noise close to the carrier. This modification was phased into factory assembled units starting with serial number 10732 and kits starting with serial number 10728. This modification kit allows you to make the simple change in the field to an existing K3 or K3S. It requires removing the KPAIO3 interface board and soldering a leaded capacitor supplied onto the board.

https://ftp.elecraft.com/K3/Manuals%20Downloads/E740287%20KPAIO3MDKT%20Instructions.pdf

YOU need the mod if the "small amount of noise" present under "lab conditions" bothers you.
I am applying it because I do everything reasonable to make my transmissions cleaner.  It is a matter of being a "good neighbor" on the public airways for me.

73,

______________________
Clay Autery, KY5G
(318) 518-1389

On 01/20/20 11:43, Russ Tobolic via Groups.Io wrote:

Now I am all confused!  I have good old trusty K3 serial #732 with the original KPA3 and upgraded with the KSYN3A.  This is the first time I have heard of this mod so do I need it? No one has told me I have a problem.   I have a handful of the 470uF caps in my junk box.

Russ, N3CO

Join Elecraft-K3@groups.io to automatically receive all group messages.