[Elecraft] KX3 Heatsinks

[Jim's Desktop]

Thanks to the confusion concerning the source of the KX3 Heatsink a 
couple of days ago, I wound up ordering the one manufactured by Pro 
Audio engineering.  It arrived this morning and I installed it in less 
than a half hour.

I think it deserves a quick review here as everything necessary was 
included including some heat sink compound.  There are three options as 
to how it can be installed.  Option 1 is no case modifications and no 
heat sink grease used.  Option 2 is "no case modifications, heat sink 
compound used on the PA transistors inside the KX3 case only.  Option 3 
requires removing the powder coating on the outside of the bottom half 
of the KX3's case in the same area it's factory removed behind the PA 
transistors and coating the area behind each transistor, the back of the 
transistors and the outside of the case in the area the powder coating 
was removed as well as the bare area on the heatsink.

I chose Option 2 and it was very easy to do without performing the 
suggested separation of the PC board from the bottom half of the case.  
After removing the KX3's original heat sink plate, carefully bend the PA 
transistors forward just enough to get a toothpick between them and the 
back of the case.  Using the supplied heat sink compound, lightly coat 
the back of both transistors and the back of the case where the powder 
coating was left off at the factory.  Carefully move the transistors 
back into contact with the KX3's case, insert the two end screws in the 
new heat sink and just snug them.  Next insert the two screws that hold 
the PA transistors, using a pair of tweezers to position and hold the 
nuts.  Once the nuts are properly started on those screws, tighten the 
other two screws holding the heat sink to the case and then tighten the 
two that hold the PA transistors.

CAUTION, one of the 4 screws supplied with the new heat sink is much 
longer than the other three.  This screw MUST be used in the hole of the 
heat sink on the side of the KX3 that contains the power connector - if 
you use it anywhere else, the KX3 could be damaged by that screw 
contacting something inside the case.  It's purpose is to pass through 
the hole used to keep the KX3's roofing filter module from coming 
unplugged if it's installed.

Operating the KX3 on RTTY used to get the back of it pretty warm if I 
did a lot of transmitting though I never bothered to check the PA 
temperature (probably should have).  Because I hadn't checked it before, 
I didn't check the temp during the "after install" test either, just 
used the feel of the case to judge.

I ran the KX3 key down for around 10 minutes at 10 watts output into my 
big dummy load and periodically felt the heat sink during that time.  
The power never folded back and I couldn't really detect much warmup of 
the heat sink after those 10 minutes so in my opinion, this one works 
just fine also.

Jim - W0EB