[Elecraft] KPA question: Gap at "S" area of heatsink pedestal

Ken Rice radiok3vv at gmail.com
Mon Aug 7 09:57:30 EDT 2006


Good friend and builder Fil Fuma is working on a
KPA100/KAT100/EC2 build.  He sent the following question to
post to the list.  Thanks to everyone for taking a look at it.

"Looking at figure 28 on page 35  of the KPA100 manual, it shows the
machined heat sink.

http://world.std.com/~rice/figure_28.GIF

There is raised section on the heatsink called the "pedestal".  It is
shown in detail in figure 35 on page 40. On the pedestal there are two
machined standoffs labeled "S". One of these standoffs is near Q2 and
Q3. I call this "S2". The other standoff is near Q1. I call it "S1"

http://world.std.com/~rice/figure_35.GIF

Careful measurements show that the board is not warped.

When the circuit board is attached to the heatsink without the thermal
pads, there is no gap between the circuit board and standoff S1.

However, there is a gap of  0.013" between standoff S2 and the circuit
board. This is because the height of the standoffs over the pedestal
is 0.085" and Q3 (and Q4) are 0.098" thick.

Is this gap supposed to be there? If not, does its existence pose
a problem -- what should I do about it?"

Thanks again!

73,
Ken Rice, K3VV for Fil Fuma


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