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.„
Before I actually started, I prepared my work space with an anti-static mat and wristband. It helps avoiding damage to the semiconductor devices due to electrostatic discharge.
Then I started disassembling the KX3:
Be sure not to overheat the encoder while soldering. According to the experts extreme temperature changes are supposed to be the reason why the viscous damping material will leak out onto the encoder.
Once soldering is complete, use pressurised air to remove residues from soldering.
For assembly just follow the steps in the opposite direction. When putting the knobs on the four encoders, make sure to support the PCB from below. The applied force may cause damage to the PCB or components soldered to it.
Despite my initial plan to replace all four encoders at once, I did only the defective one. Desoldering was tricky and would have been really difficult for at least one of the remaining encoders. So I decided to wait until the next encoder fails – hopefully not on a summit 😉
Edit: Scott, N9AA, suggested to use Chip Quik (which I haven’t heard of before) for desoldering the encoders. It reduces the melting point of the solder significantly and is usually used for desoldering large IC’s. There are some videos on YouTube. I haven’t tried it so far but I’ll post it here once I tried it.