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. Then, for unknown reasons, it worked again.
The full story and the reply from ELECRAFT can be found on my blog:

73, Roman - DL3TU

I had an encoder die on my PX3 which Elecraft replaced for a small fee.

I’ve always been impressed with Elecraft’s service from kits to factory assembled products.


Yes, Paul, their service is amazing. Within 24 hours the root cause was found and spare parts were ordered.
Alas, the shimpment costs will exceed the material costs by far :cry:

73, Roman - DL3TU

edit: after 36 hours the parts are already on the way…

Hi everyone,

I just added a description of how to replace the defective encoder. It’s on my blog:

Hope no one needs it :wink:
73, Roman - DL3TU


Thanks so much for posting this, it really helps me. I’ve done many winter acrivations and have had to deal with this problem. I complained to Elecraft some time ago and their response was that I has operating below the published specs for operating temp (something like 32F/0C), so they didn’t acknowledge the problem.

Kevin AC2KL

Not a fault as such, but I’ve found that the encoders on my KX3 slow down at around 0°C. Perhaps the latency changes or something, but I have to turn the knob quite slowly to get the value to change on-screen, too fast and it just jitters and stays roughly the same. I don’t specifically expect my KX3 to work flawlessly sub-zero, I read once that laptops are often warmed up to above zero in the Arctic regions before being turned on, otherwise condensation becomes a problem. Are some electronics designed to work at sub-zero temperatures?
73 de OE6FEG / M0FEU

My KX2 exhibits that behavior as well when it’s sub freezing.

+1. I have this behavior as well in cold temperatures with my KX3 (SN 957). It doesn’t affect the main VFO encoder, but does affect the B encoder and to a lesser extent the Keyer/Mic/Pwr encoder. I find it very annoying sometimes, but haven’t found a solution other than Matt’s “turn the knob quite slowly”.
73, Malcolm VE2DDZ

Apparently given the everlasting winter here (it snowed last night) it might be more than just sometimes!

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The VFO-B encoder on my KX3 SN 7113 also skipped when turned too fast. I first noticed the problem when doing the extended temperature calibration after building it, but it may have been broken from the beginning. It malfunctioned at all temperatures when turned fast, but was reliable if turned slowly. I just “turned slowly” for a year or so, but then finally sent it in (after playing with a friends good one!). They replaced all 4 of the small encoders & it now works great. I was happy to have Elecraft fix it. I would have sent it in when still under warrantee, but I was having too much fun!

Rob - AE7AP

So there are three scenarios:

  1. Encoder fails at or below 0°C but works if turned slowly. At higher temperatures it works as intended.
  2. Encoder fails at any temperature but works if turned slowly. The defect is permanent
  3. Encoder fails completely in a temperature range between 10°C and 20°C (at least). But not all the time.

It looks like replacing the encoder works for scenario 2 and 3. I wonder if there is a workaround for scenario 1. If this happens because the encoder is operated outside its specified temperature range, I don’t see many options.

Anyway it’s a quite interesting case…

73, Roman - DL3TU

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I recommend asking this question on the Elecraft email reflector. The people who designed the radio read that.



Oops, I see the exchange with Elecraft is in your blog post. Clearly, people didn’t read that, because they are discussing things that are answered there.


I’m trying to think what the failure could be on an encoder that is related to temperature. I’m assuming these have a pair of “slots” and do quadrature encoding so you can see which way it’s turned and how fast. If it becomes rubbishy at low temps is the LED/opto that is failing (low output or low sensitivity) or is it mechanical and the slots are changing size or moving with contraction.

Till I read this thread I never even thought about temperature effects on these encoders.

This is the response from Elecraft, copied from DL3TU’s blog.

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.


I must say, I find my KX3 perfectly usable in the cold, it’s just a quirk as far as I’m concerned. But it raises the question: what kind of temperature range is reasonable on a portable radio?

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in the meantime I took the defective device apart. To my big surprise it turned out to be a contacting encoder rather than an optical one as mentioned in one of Elecrafts emails.

Here’s the evidence:

Most likely its this one:

The operating range is specified from 70°C to -30°C. So it should not be the encoders causing the issue - except some of the viscous fluid visible in the first picture gets on the contacts and causes high resistance at low temperatures (?)

Anyway, I agree with Matt.

73, Roman - DL3TU

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Hi Roman,
Can you please contact me off list about your experience replacing the encoder in your KX3? I need to replace one in my KX3 and wanted to ask a question or two. Thanks!
Scott N9AA (at) arrl (dot) net