[Elecraft] The K2 Kontest Kooler

[Lee Buller]

After operating my K2/100 on the 10 meter CW contest, I decided to develop 
a plan to get additional air flow across the heat sink.  Calling CQ to run 
rate gets the heat sink pretty warm (hot) to the touch even when the fan is 
running all the time.  I had to dig up an old muffin fan from my linear 
construction days and blow some air across the heat sink.  But it was ugly, 
noisy and wasn't cool. (no pun intended)  There had to be a way to get more 
air across the heat sinks

The result was The K2 Kontest Kooler.

Simple instructions

Parts

All the parts are at your local hardware store except for the fans.

1.  Aluminum angle piece (you can also use a wooden piece of corner 
moulding stock, but the aluminum stock was $1.00 cheaper than the wood 
moulding.  I used 1/2" angle stock.

2  Four bolts, four nuts, four lock washers.

3. Three to four felt pads with adhesive on the back (purchased about 30 
for $2.00)

4.  Two fans of your choice.  I  found two small fans that were on Pentium 
233 heat sinks and are ideal for the job.  The ones I got were 2" or 5 cm wide.

Instructions.

1.  Cut the aluminum angle stock 7.5 inches.  Try to cut straight and true 
with a hack say.  File the edges so there are no burrs.

2.  Measure 2 1/8" from either end and make a mark

3.  Center the fans on these marks and mark the hole which you will mount 
the fan to the aluminum angle stock.

4.  OPTIONAL:  Now a small amount of the fan blades will be below the top 
of the aluminum angle stock.  You can take a Dremel tool, nibbler tool, or 
a file and round out the area where the blades suck air through.  I am not 
sure you even have to do this as what part of the fan is blocked is very little

5.  Drill four holes where you marked to match the hardware you have.

6.  Mount the fans with the air going away from you on the aluminum angle 
stock on the "inside" of the aluminum stock.

7.  Place three or four self adhesive felt pads to the aluminum angel 
stock.  The felt pads cushion the aluminum stock and save the K2 painted 
service or the material on the heat sink.  I think it would act also to 
lessen the fan vibration.

8.  Wire the two fans together (red to red - black to black) and then 
connect that to your 13.8 power supply.  The fans should turn on when you 
hit the PS switch

9.  Place the K2 Kontest Kooler on top of the K2 at the front pointing to 
the back.  Or, place it on the back pointing to the front (This irritates 
my eyes).  Or place the K2 Kontest Kooler on the left side or the right side.

Optional Modifications

If you want the fans to run slower, place a resistor in series with the 
fan.  For instance, I have two fans that pull 150 ma and 60 ma for a total 
of 210 ma.  To lower the voltage and lower the speed you can place a 
resistor in series with the fans.  Testing the fan at 10 volts the fan ran 
slower and quieter.  Therefore, you would calculate the voltage drop at 
13.8 v - 10.0 v = 3.8 v.  Since R=E/I the resistor you could use would be 
3.8v /.210  which would be around 18 ohms.  The power rating would be P=I*E 
or about a 1 watt resistor.  I hope all the theory is right here.  It has 
been a long time running Ohms Law.

One could get really fancy and use an LM34 (I think that is the right part) 
to place on the heat sink.  You can set up the LM34 to a couple of 
transistors that would turn on the fans when the temperature hit a certain 
point.

One could even put on a pot to control the speed of the fans.

One other item, you might want to paint the aluminum angle stock Elecraft 
colors.

Nothing is attached to the K2.  No adhesives, no drilling, no mods of any 
sort.  Keeps the heat sink cool when your running rate in a contest.  If 
your are not running a contest or PSK31 or RTTY, then take the K2 Kontest 
Kooler off and stick in a drawer for when you need it.

The fans I got were pretty old and I have to "oil" them up.  You can get 
them pretty cheap on the Internet.  Radio Shack's fans are very 
expensive.  Scrounge them at all costs.  Check your local computer store 
and I bet they could give you some.  They might be dusty and dirty.  Clean 
the off very good because dust and dirt really affects the air flow a fan.

Hopefully, pictures will follow in a week or so....

Flames to me

Lee - K0WA