[Elecraft] K3 Assembly issue with bottom Heat Sink cover!

[Dr. James C. Garland]

Rodger,
I assembled my K3 a couple of weeks ago (s/n 1217), and did not experience
your problem. The three transistors clamped nicely against the (thicker)
bottom cover using only the hardware specified in the instructions. As I
recall, there are both 3/16" and 1/4" screws in the kit. You sure you've
used the correct screws everywhere?

Took me about 10-11 hours to assemble my K3 (100W). I'm amazed you could do
it only 4 hours!

73, Jim W8ZR

 
> Hey gang,
> 
> Just spent 4 hours assembling K3 s/n 1318 and all went well except for one
> slight but potentially serious hardware problem.  When installing the
> bottom heat sink cover over the LPA I noticed that the required 4-40 x
> 1/4" screws bottomed out in the standoffs under the TO-220 LPA transistors
> before they would compress the cover to the transistors (and yes I can
> measure screw lengths).  This will leave a gap between the transistor and
> the heatsink and not provide proper heat sinking!  It is strange to note
> that one of the Manual Errata changes was to point out that the heat sink
> cover was "slightly" thicker than the other bottom cover.  Wonder if this
> part has changed?  Any way, I added 3 #4 stainless steel flat washers
> under the screw heads and that allows the screws to fully compress the
> heat sink against the transistors.  For a belts and suspenders fix I also
> added a dab of heat sink compound to the transistors as well.  I did not
> check the screws coming from the top side of the LPA assy to see if the
> factory may have used the wrong/longer screws
> taking up extra standoff threads.  A #4 split washer could have also been
> left off of this top side screw and create the same issue or tol. stack up
> of the parts?
> 
> Any way HEADS UP!
> 
> 73,
> 
> Rodger
> N4NRW
> ft.com