[Elecraft] Installing the Q7, Q8 Mounting Parts

[Steven Pituch]

Hi all,

I ordered 2 shoulder washers, 2 spacer washers, and a bunch of the soft 
plastic thermal insulators from Elecraft so I can finalize the job of 
doing the upgrade mods on K2 #402.

I was just wondering about the theory of this layout.  The tab of the 
transistor is pressed against the thermal pad by the spacer which is 
tightened by the mounting screw.  I guess you need to only tighten it so 
much as to not puncture the soft insulator.

I am confused because there is a 2-D fastener at this location situated 
in such a way as to appear to be a spacer.  If the 2-D fastener actually 
governs the height of the circuit board above the case heat sink, then 
tightening the screws for the transistor heat sinks would not work 
because the 2-D fastener would prevent the movement.  Tightening the 
screw would only warp the board.  If the 2-D fastener did not restrict 
the tightening of the heat sink screws then why are they there?  You 
would think the 2-D fastener would be the exact height to prevent the 
plastic insulator from being over-compressed, but it doesn't seem to be 
that way.

My old spacers are so warped, probably from heat, that they look like 
truncated cones, wider at the base.  My guess is that in this state they 
were not putting any pressure on the transistor tab to force it into the 
plastic insulator.  In that case its a wonder I didn't burn the 
transistors out.

What about using a mica insulator?  That would never puncture.  Is mica 
worse at being a thermal conductor than the soft plastic ones used in 
the K2?

72,
Steve, W2MY