Replacing Elecraft K3 Push Button Encoders

For a couple of years I’ve had problems with the CMP/PWR encoder on my K3. When I needed to reduce power to use my amp or increase power back to 100 watts I’d have to twist and twist the power control. Recently there was a thread on the Elecraft reflector of someone else having problems with one of their encoders. That prompted me to finally replace my faulty encoder.

I called Elecraft to order the encoder. Elecraft recommended replacing all four encoders. They also recommended returning the rig to them so they could do the work as well as apply updates to the rig. With the cost of shipping the rig to and from Elecraft and the repair cost I decided to try to replace the encoders myself. I ordered the four encoders at a cost of $3.34 each plus $3.50 shipping.  The envelope the encoders came in showed the Elecraft P/N as E640018.  Also written on the envelope was “Encoder, 80 counts, w/PB switch”. There’s no indication on the old or new encoders of the manufacturer or part number. Update 10/3/2019 – OK1RP posted to the Elecraft reflector that P/N E640018 is a Bourns PEC11R-4015F-S0018 encoder.

My K3 is SN 3329 purchased in August, 2009. The encoders in my rig are smooth with a slight amount of play. My club has a K3 purchased in March, 2009, that has encoders with slight detents. I prefer the feel of those encoders over mine. Unfortunately those encoders are no longer available. The replacement encoders are smooth but don’t have the play of my original encoders.

I built my K3 and have added a number of accessories over the years so I’m familiar disassembling and assembling the rig. However, I haven’t had it apart in a while so I used the DVR installation manual to refresh my memory on disassembly and the original assembly manual for removing the front panel board from the front panel. Once I had the front panel board out of the front panel and had a good look at the encoders I began to wonder if maybe I should have sent it to Elecraft.

There is an LED board that is around the SHIFT/LO – HI/WIDTH encoders making access a bit of a challenge. The CMP/PWR encoder that was faulty is easy to access so I decided to replace that one and then decide if I could do the others. Rather than unsolder the CMP/PWR encoder I just clipped the leads except for the large body ground lead I couldn’t reach. With the other leads clipped I just unsoldered that one and removed the encoder.

When I ordered the encoders Elecraft alerted me that they must be mounted slightly above the circuit board so the push button function will operate correctly. I looked around for something to use as a shim/feeler gauge and found a tie wrap that was just the right thickness. (Update 3/17/15 – Mark, WH7W, wrote to me with the following information: “Elecraft has put small plastic washers beneath the encoders to provide the required board clearance needed so I did not need to use your tie-wrap feeler gauge trick.”)

I installed the CMP/PWR encoder. I found all the solder had to be cleared from the rectangular holes for the larger case ground terminals. Also the bend in those terminals had to be straightened before they would fit. The encoder stayed in place with a friction fit. I then used my tie wrap feeler gauge to set the spacing and soldered two of the pins on opposite sides of the encoder. After checking the spacing again and eyeballing the encoder against the other encoders I soldered the rest of the pins.

Since replacement of the CMP/PWR encoder went pretty well I decided to do the HI/WIDTH encoder next. It’s surrounded on three sides by the LED board making snipping the leads only possible for three leads. I used my EDSYN desoldering tool (solder sucker) to desolder all of the leads. I was wondering if it would be able to pull the solder from the encoder side of the board but it did. Same procedure as before for installing the new encoder. For the last two encoders I just snipped the leads I could reach, heated the remaining leads, and pulled the encoder free.

I reassembled my K3 and did the smoke test. Everything worked as it should. I like the feel of the new encoders compared to my original encoders. I should have done this repair a couple of years ago!

Update 8/15/2021 – A few weeks ago I replaced the encoders in a friend’s 2009 vintage K3. Since I had done it once before I’m now an expert!

I now have a Hakko FR-300 desoldering tool. That worked great on the five small leads but while it removed some of the solder on the two large tabs it wasn’t enough to pull the encoders free. For those I either snipped the large tab or alternated heating one and then the other and rocking the encoder until I could remove it.

For the spacing of the encoder from the circuit board I found a post on by Keith, WE6R, who is an Elecraft K3 Tech. Keith stated “Encoders Elecraft part# E640018, nylon washer as spacer underneath,Washer, Flat, Ny, 0.375″ x 0.047; E700187 or E700035 or E700045.┬áThickness not too critical.”

I purchased a 3D printer a couple of months ago so decided to try to print some spacers. I ended up using 1.4mm spacers x 8mm diameter. A bit larger diameter would have been better.

Yesterday I was about to toss the old encoders but then decided to pry one open. Below are pics of what the inside looks like.

Original Encoders
Side View of Encoders
Solder Points
Left – Old, Right – New
Left – Old, Right – New
New Encoders Installed
Shaft Side of Encoder
Rotating Pulse Contacts
Encoder WIper
Plastic Disc Covering Switch
Metal Spring Disc
Switch Contacts