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K2 Impressions – Part 10 – Kazmo’s Kustom Kreations

A Cool Accessory – aka Outboard Heat Management Project

The first extended period of use for the K2 came about during Field Day 2008. The top panel of a K2/100 is essentially one big heat sink. It soon became obvious the the K2 gets quite warm under continuous use – like when calling CQ endlessly for Field Day. The temporary FD solution was to re-position the fan to cover both the K2 and the operator.

Ten-Tec has a 12v external fan accessory, but it seemed like a good project to fill in the “waiting for family to get ready….” time.

I located a 3×6 heat sink that had been recovered from a dead computer CPU. As luck had it the heat sink had two parallel ridges along the bottom. Even luckier still, these ridges aligned well enough with the top of the K2 heat sink that it more or less “snapped on” to the top of the K2. The extra heat sink alone cooled the K2 a lot.  But a fan would help.

Having a couple of four inch pie fans in the junk box, also recovered from computers, I was on my way to a ten minute project.  Adding a couple of 5 inch rails cut from aluminum angle stock, a few nuts and bolts, and a dab of “JB Weld” epoxy, we get a nice heat sink/fan mash up. The K2 is now cool as ice. Functional – not esthetic!

Top view of the Fan/heat sinkTop view of the Fan/heat sink

Briefly, the fan is bolted to the aluminum angle. The angle is then epoxied to top of the the external heat 3×6 sink. A resistor is in-line to drop the fan speed by about half. The fan used is rated at 12v and 0.29 amps. Gathering a few half watt resistors, I came up with a 75 ohm 2 watt resistor. Putting the resistor in-line slowed the fan down and cut the fan noise completely. It still pushes plenty of air through the external heat sink. 75 ohms seemed to be the magic value needed to reduce the rpm’s “just enough”.  Even very slightly higher resistance values cut the fan off completely. The whole fan mash up still is a snap-on, snap-off accessory – nothing changed on the K2.

Heat Sink - SideHeat Sink – Side Ready for CoolingReady for Cooling

? Custom Knobbery ?

There is lots of chatter over the years on the Elecraft mail list about a good replacement knob for K2. The stock knob is fine, but a slightly larger knob seems to work more to my personal tastes. The knob installed is from a Yaesu FT-840.

K2 customizedK2 customized

The stock 840 knob has a plastic skirt, which can be seen in this RigPix photo. With the skirt left on the knob the display is obscured so it has been removed before installation on the K2. It appeared to have been held on it only a few drops of glue, so it could easily be re-installed later. That’s not an issue in this case, since the FT840 was involved in an unfortunate incident during a thunderstorm. 😮

The FT-840 knob is a perfect match to the Elecraft. It has a good feel, the tuning rate is slightly slower, and it even comes with its own “dimple”. Perfect. The 840 had a long shelf life, so this knob may be stocked for a while yet.

This knob would also be an improvement on the K3. I found the tuning on the K3 similar to the stock K2.

-more- at the K2 Impressions page

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