[Elecraft] KFL1-4 Trimmer Cap Replacement

[Phil Wheeler]

Mike wrote:

>Phil Wheeler wrote:
>
>>retrofitted the newer trimmers into my K1/KFL1-4, and realigned that
>>
>
>Hi Phil,
>
>Would you have any tips on the best way to approach removing the old
>trimmer caps without hurting the PCB?   I'd love to make this mod to my
>early KFL1-4, but the task of getting the old trimmers off is a bit
>scary.  I suppose one would be better off cuttting off the old trimmers
>rather than trying to remove them intact.
>

Mike,

I ordered the new trimmers (paid $12 extra to have them sent overnight 
becuase I thought I would be traveling with the K1 this weekend) and 
then set about removing the old ones very slowly.  I first removed as 
much solder as I could with wick.  Then I reached in with a hemostat and 
pulled up on one side while I heated the pad, then the other -- and 
finally wicked out the remaining solder.  This generally worked well -- 
though I did damage one pad so the lead of the new cap would not quite 
fit (so I used a very fine file from an RS set to narrow that lead ever 
so slightly).

I'm not sure you can cut off the old ones because they are VERY 
inaccessible due to nearby taller components.  If you can, that would be 
a good approach.

Installing the new ones is a bit tricky, becuase visibility is not too 
good with the stuff around them.  The new ones have a pretty pronounced 
bend to let them snap into the holes.  But after I crumped a lead on a 
couple of them, I used fine needlenose pliers and straightened all the 
leads -- and then bent the leads on the bottom of the board to hold them 
in place for soldering.

Re the following: I've made none of these mods, that I can recall.  The 
AGC has never bothered me and I mostly use the rig with the internal 
speaker..

73, Phil

>
>I also need to make the ATTN pop elimination mod (with 10 uH RFC), plus
>my AF gain control has gone scratchy already and needs replacement.
>
>I've had a chance to examine the schematic of the "new" generation K1. 
>I see that the "real" circuit improvements (as opposed the two changes
>that support transient test configurations) of the latest model seem to
>be limited to the ATTN pop mod and the VFO linearization mod.
>
>I was surprised there were no changes made to the AGC circuit response
>time, since most people report better performance from a C31 that is 1
>uF or smaller.
>
>I would have liked to have seen a simple PCB trace design change in the
>new K1 that would allow removal of one jumper to disconnect the ring on
>the phone jack, so that mono phones and speakers could be plugged in
>without using an external stereo-to-mono adapter.  My K1 required a
>couple of PCB trace cuts and a jumper installation just to disconnect
>the ring.  Because there are no PCB trace diagrams in the K1 manual
>(obviously a most serious omission from any kit building manual), it
>took some trial and error following construction to determine which
>traces went to the ring.
>