[Elecraft] K3 Mods - Unauthorized Shortcuts

[Bill W4ZV]

        I finally got around to installing mods in units #1361 and #2183. 
The latter only needed a few mods but #1361 (including KRX3) needed the
following:

K3 AF Mod (K3AFMDKT)
K3 Synthesizer ALC
K3 AF Output
KPA3 12V Sense
Front Panel Mike Circuit
Rear Panel RS-232/Audio RFI Immunity

These shortcuts (not authorized by Elecraft) worked for me in the following
order:

1.  I did the RFC47 part of K3 AF Mod (K3AFMDKT) first by removing the top
and bottom front covers.  As others have previously noted, it's possible to
remove RFC47 from the bottom without removing the KRX3 to gain access to the
top side of the board.  I used a Radio Shack solder sucker to remove solder
from the bottom holes but my existing RFC47 did not drop out the other side
as some have reported.  I used a fine point to push the leads down and then
grabbed the RFC with needlenose pliers from the top side.  Once RFC47 is
removed, it's a simple job to install the new one in the existing holes on
the bottom side.  Later you'll install the resistors that go on KIO3 when
you get to step 5 below.

2.  While you have the bottom front cover off, you can install N8LP's R8/R9
mod to improve IF out sensitivity (see the LP-PAN Yahoo group files for more
info) and also, if you have an older unit, the Hardware AGC and CW Keying
Rise Time mods since they are in the same area of the RF Board exposed by
removing the bottom front cover.  When you finish, reinstall the bottom
front cover.

3.  To do the Synthesizer ALC mod, you add a 180k leaded resistor to the
synthesizer board(s) mounted on the front panel.  By carefully cutting and
forming the resistor leads, it's possible to insert them into existing holes
on the synthesizer board(s) and then carefully solder each end, making sure
that the leads extending through the boards are not long enough to short to
the front shield.  In my case I also removed the top TMP cable from the left
(KRX3) board to avoid the possibility of nicking it with my soldering iron. 
I felt this was much easier than removing the KRX3 and synthesizer board(s)
per the instructions.  CAUTION:  If you're not sure this mod has been done,
you'll need to remove the synthesizer board(s) to confirm that R10 on the
board has not already been changed to 56k.  With the boards in place, you
cannot confirm this by measurements alone.  I was sure my synthesizer boards
had not been modified because of the age of my units. 

4.  Next I removed the left side cover (with the handle) to expose the back
side of the front panel MIC connector.  To install the Front Panel MIC
modification, you need to ground Pin 7 by running an insulated wire from it
to a nearby ground as shown in the mod instructions (right side of Fig 11). 
If you have a thin soldering iron, it's possible to do this without
disassembling the front panel (which is a pain to reassemble).  Confirm that
you have not shorted any adjacent pins and also check the the center pin of
the MIC connector shows a short to the outer shell.  Leave the top and side
covers off.

5.  Now remove the KIO3 and install all the components as instructed in the
K3AFMDKT, Rear Panel RFI Immunity and AF Amplifier Output mods.  I found it
easier to remove KIO3 with the side cover off after step 4 to avoid
interference with a TMP cable going to the KXV3's IF OUT.  After you finish
the side and top covers can be reinstalled.

6.  The 12V Sense mod can be done by removing the 4 screws holding the fan
assembly and letting it drop enough to give you access to install the diode
on the KPA3.

        The procedure above is NOT AUTHORIZED by Elecraft and you shouldn't
attempt it unless you have the proper equipment (a thin ESD-safe soldering
iron like the CSI/Hakko 936, good lighting, magnifying visor, ESD work
surface, etc) and soldering experience.  But it worked for me and might be
of some help to others.  Proceed at your own risk!

73,  Bill  W4ZV



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