While operating on DM/BW-852 I encountered an issue with the Keyer/Mic- encoder of my KX3. A detailed description can be found here: Link
Elecraft support confirmed the encoder being the root cause :
„We […] do know that extreme temperature changes, more typically found with the KX2 and KX3, may cause shorter life spans for them. The most common failure mode we see with the encoders is that the viscous damping material used in the shafts will leak out onto the encoder itself, which in turn, causes them to fail or skip as the encoder is turned.„
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.
Most likely the encoder is from Bourns. The data sheet can be found under this Link.