Elecraft K2 PLL - Manual (Page 3)

Page 3 of 4
If you determined that you need to remove X1 (and X2, if present): (1) Heat and lift the ground lead soldered to
the side or top of X1. (2) Alternately heat each of the crystal leads on the bottom side of the board while gently
rocking it back and forth on the top until it falls out. (3) Remove X2 in the same manner (if X2 is present).
Locate resistor network RP3, which has 8 pins and is near X1 and L31. RP3 must be removed. First, bend it back
and forth until the leads break. Then, from the bottom side of the board, heat each of the leads with a soldering iron
and gently remove them using long-nose pliers.
Using solder wick or equivalent, clean out each of the holes that was used to mount L31, RP3, X1 and X2. This
includes the two ground holes for X1 and X2.
Install the new crystal at X1. The crystal should be mounted flush to the circuit board and the leads trimmed so
that they are nearly flush with the circuit board.
Solder the ground wire to the side of X1. (Remove the ground wire for X2 if present.)
Install the new L31 on the bottom of the board. The new L31 looks identical to the old one except the value is 12
H. The inductor should be installed so that its body is flush against the circuit board.
The thermistor board will be installed at RP3's location. Slide each of the 8 leads of the thermistor board through
the corresponding holes at RP3. The components on the circuit board should be facing U6, and the thermistor
should be oriented toward X1. (See photo, page 4.)
Once all of the leads are inserted, slide the board so that it is flush against the RF Board. It may be necessary to
bend the thermistor board toward U6 slightly so that the solder joints on the bottom of the RF board can clear C87.
The thermistor board and its parts should not be touching U6 or its pads.
Make sure that the edge of the thermistor board is contacting the RF Board along its full length, or there may not
be enough clearance for an audio filter option (which mounts on the Control board). Solder the eight connections
on the bottom side of the RF Board.
If your K2 serial number is lower than 3000, make sure you have installed the BFO modification (BFOMDKT).
One of the items supplied in this kit is a 2.7-k resistor. This resistor, designated R19, must be soldered across pins
7 and 8 of resistor network RP2 (in the PLL area).
If you have an older K2 (early revision A or Field Test), you may have a 100 k resistor network installed at RP2,
which is in the VCO area. If so, you'll need to solder two 10 k to 12 k resistors across RP2: one across pins 1-2 and
the other across pins 3-4, on the bottom of the board. (There's no need to remove RP2, which can be difficult. The
paralleled resistors will suffice.) Any type of 10 k to 12 k resistor can be used; 1/8th watt or 1/4 watt, any
tolerance.
This completes the installation of the PLL reference oscillator upgrade. Check your work to make sure there are
no shorts between added components and other parts of the K2 circuitry.
Reinstall the side and bottom covers on the K2. Reinstall the Control Board.
Alignment and Test
Connect the K2's internal frequency counter probe to test point TP3 (PLL reference oscillator).
Turn on the K2; it should power up normally.
In the Menu, locate and activate CAL Fctr as described in the K2 owner's manual. You should see a reading on
the frequency counter. When you tap BAND- the counter should read about 12085 kHz. When you press BAND+
the counter should read about 12098 kHz. The difference between these two readings must be greater than 9 kHz.
If this isn’t the case, there is something wrong with the modification.
Connect the frequency counter probe to test point TP1 (VCO).
Install the top cover, and allow the K2 to warm up for at least 30 minutes at room temperature.
Switch to 40 meters and run PLL CAL as described in the manual.. Note: If you have firmware revision 2.00 or
later, CAL PLL is run only on 40 meters, not on each band. If you have older firmware (revision 1.XX), we
strongly recommend that you obtain an upgrade, as VFO tuning linearity has been dramatically improved.
If you installed the BFO modification but have not re-aligned your BFOs, do so now.
This completes alignment.