KX3 encoder issue

While operating on DM/BW-852 I encountered an issue with the Keyer/Mic- encoder of my KX3. For about a minute it wasn’t possible to change the keyer speed. Luckily the speed was set to a reasonable value (20 wpm). Then, maybe by touching the knob differently, it worked again.
A couple days ago, when preparing the activation, I had the same issue while trying to reduce the KX3’s output power. I pushed the button (the display showed 10 W) and turned the knob. The reading went down to 9.8 and stayed there regardless of any further turning. I switched to „keyer speed“ by pushing the knob (which actually worked) and tried to change the keyer speed to no avail. Then I switched back to output power and turned the knob again: the encoder did not work. Even after switching the KX3 off an on, it remained in this state.

Next I opened the KX3, took out the CP- board and did some resistance measurements at the back side of [Z4]. Now the encoder seemed to be working again. After assembling the KX3 everything worked smoothly.

It looks like the encoder has an issue. But before I replace it (or even all four of them) I asked the experts at ELECRAFT for a confirmation. The reply arrived within a few hors (!)

„Hi Roman,
Thanks for the contact.  To your questions on the KX3 encoders, we have received reports of some encoders losing some of the damping fluid that is embedded into the shaft and sleeve.  These are sealed but can leak.  When this happens, some of the fluid will get into the optical encoders and cause the symptoms you are seeing.
Generally, we recommend all 4 be replaced at the same time to save having to do them individually.  We do this with the K3 and K3S encoders in much the same way.
The KX3 encoder is Elecraft part #E640018 at $2.08 each.“

The encoders are already ordered and will be replaced as time permits. Thanks ELECRAFT for the fast support!


In the meantime, I took the defective device apart. To my surprise it was a contacting encoder rather than an optical one.

There is some fluid visible in the picture above. If this gets on the contacts it could cause trouble.


Most likely the encoder is from Bourns. The data sheet can be found under this Link.


KX3 Go Box

Having played with the KX3 for a couple of weeks I wanted to try it outdoor. But hiking comprises a certain risk for the equipment: Humidity from rain and snow, vibration and shock from other items in the rucksack can cause harm to the rig. The first attempt with bubble wrap basically worked, but was not to my complete satisfaction. A box was needed!

I searched the web for availalbe solutions (which are quite a few) and found Tom’s great Go Box:  http://www.oe2atn.at/tom/gobox/ – the most professional one I found.

However, I had something different in mind: The Go box should look understated in order not to attract thieves on a stay on a camping site. It should also be as light as possible. By accident I tripped over an old first aid box, big enough for the KX3.


With a few pieces of foam and some glue the protective padding was made.


The KX3, a short power cable, earbuds and the Palm Pico Paddle fit nicely into the box.



[2018-04-02]: Removed the foam in the lid to overcome the VFO-A encoder issue (see description below).

[2020-05-01]: Added a check list in the lid and a cavity for pencil and pencil sharpener in the foam.

KX3 Go Box

VFO-A encoder issue:

From time to time, while turning the dial, I noticed that VFO-A seems to get stuck at a certain position. The frequency reading in the display „jumps“ back several 10 Hertz then moves on and „jumps“ back again  This can happen several times. Suddenly the failure disappears and the VFO works as intended.

This video from KC9W describes exactly my situation: https://www.youtube.com/watch?v=COPj2skxWys
One explanation is that the old version of encoder is responsible for this behaviour. But taking a close look revealed that my KX3 already has the new encoder version. (Link to ELECRAFT’s KX3 VFO Encoder FAQ). Other possible explanations for this weird behaviour suggest excessive mechanical stress to the encoder.

When opening the Go Box, I found that the VFO-A knob leaves a mark in the foam in the lid. Possibly, if compressed that much, the foam transfers pressure to the VFO-A knob and the encoder.

As a counter measure I removed the foam from the lid. Now there is some space between lid and VFO-A knob even if the lid is closed. Instead, I put a large piece of foam on top of the bezel. If the lid is closed the foam will be compressed and keeps the KX3 in its place. But it no longer applies any pressure to the VFO-A knob.
In order to finally solve the encoder issue I had to replace the encoder.