[Elecraft] KFL1-4 Trimmer Cap Replacement

[Mike]

lhlousek wrote:

> I replaced all the trimmers on my KFL-4 with no difficulty.

Well, that's encouraging!

> It was well worth the effort because my K1 would lose more than half
> its power on some bands with a ambient temp decrease of only 10 F

Sadly, it appears that this non-trivial mod is mandatory.

Recent measurement of power output on my K1 shows that the KFL1-4
alignment has shifted all over the place.  Thus, my K1 right now is
"hors de combat."  I may put back the 20/40m two-band board until I can
replace the trimmers on the KFL1-4, because the KFL1 with the original
caps behaves so poorly with regard to maintaining its transmit
alignment.  It's a shame this characteristic wasn't caught in the beta
testing of the KFL1-4, for it's not going to be easy to replace the 16
defective trimmers without running a real chance of hurting the PCB or
nearby components during disassembly.

I use the 170 kHz VFO option.  I've never been able to align the KFL1-4
such that 5 watts output can be produced over the complete VFO range on
40m the way the old KFL1 20/40m board could.  When I rebuild the my
KFL1-4, I'll also increase the size of the coupling capacitors C10 and
CK in the bandpass filters for 40/30m to broaden the alignment for 40m,
using values recommended in the KFL1-4 temperature stability application
note (5 pF).

Mike / KK5F