ELECRAFT K3, KSYN3 Modification Manual

Elecraft K3

KSYN3 DDS Gain Modification

Revision A1, May 27, 2010

Copyright © 2010, Elecraft, Inc., All Rights Reserved

The KSYN3 synthesizer uses a direct digital synthesizer (DDS) circuit. In rare cases, at certain frequencies the
DDS driving signal to the Phase Locked Loop (PLL) may be marginal, resulting in a sudden shift in frequency
(commonly called “chirp”). This modification adds a resistor to the KSYN3 board that increases the DDS drive
level prevent this condition. This is an optional modification and is not required unless you are experiencing this
condition.

If you chose to make this modification and your K3 is equipped with the KRX3 subreceiver it will have two
KSYN3 synthesizers. Although only the main synthesizer is used for transmitting, both boards should be
modified to in case they are reversed at some future date.

This modification involves adding a single leaded resistor to the pc board. No SMD work is required. If needed,
the resistor may be ordered from Elecraft. See Parts Required below.

Tools Needed

A temperature controlled ESD-safe soldering iron with a fine tip and fine rosin core solder, diagonal cutters and
Phillips screwdrivers for opening the case and a DMM for making resistance measurements. An ESD wrist strap
is strongly recommended.

Does My K3 Have This Modification?

If the modification was made using a leaded resistor as described in this document, the resistor will be visible on
the side of the KSYN3 board closest to the front panel shield. You need to loosen the KSYN3 board mounting
screws and tilt the board away from the front panel shield slightly to see the resistor. If the resistor is not
present, you may have a board that was modified at the factory by replacing a SMD resistor. In that case,
measure the actual resistance as described under Installing the New Resistor on page 3.

Parts Required

Photo Description Quantity Part

Number

Resistor,51 ohms, 1/8 watt, (grn-brn-blk) 1 E500415

Elecraft • www.elecraft.com • 831-662-8345

Removing the KSYN3 Board(s)

Remove the K3 top cover as shown in Figure 1.

Whenever you remove screws from a panel, if one screw seems too tight to loosen

without damaging it, first loosen the other screws then try again. Sometimes one screw
binds in its hole when the other screws are tightened

Figure 1. Removing the Top Cover.

.

CAUTION:

before touching components or circuit boards inside the K3.

If you are modifying the main KSYN3 board (see Figure 2) and the K144XV 2-meter option is installed,
remove the K144XV module. Remove the three screws securing it to the right side panel. You can move it out
of the way while removing the synthesizer or you can unplug the connectors and set it aside.

Remove the KSYN3 board(s) to be modified (see Figure 2). If the optional K144XV 2-meter module is
installed, remove it to gain access to the mounting screws for the main KSYN3 board. Each board plugs into the
RF board on bottom of the K3 and is held in place with two screws at the top. Loosen the screws and tip the
boards to remove the split lock washers. Unplug the TMP coaxial cables as you lift each board out. The TMP
connectors are held by friction. Pull only on the metal ears of the TMP plug. Do not pull on the coaxial cables.

Touch an unpainted metal ground or wear a grounded wrist strap

Figure 2. Removing the KSYN3 Boards.

K3 KSYN3 Gain Modification Page 2 of 5