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

[AC7AC]

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[Bill W4ZV]

Ron D'Eau Claire wrote

Bill Wrote:

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!

---------------------------

Surely Bill was referring one of the other procedures he noted.

The 12V Sense mod *recommends* only removing the fan panel assembly. No
further disassembly is needed.

Yes my caveat was for "all of the above".  :-)

73,  Bill