ELECRAFT K2 - Page 4

VCO (Voltage-Controlled
Oscillator) Test
VCO Alignment
In the following steps you’ll adjust the VCO inductor (L30) so
that
Use
BAND +
or
BAND
-
to select the 80-meter band, and set the
the VCO control voltage is in the proper range.
VFO for a frequency of about 4000.10 kHz.
Disconnect the internal frequency counter probe and remove
Connect the frequency counter probe to the VCO test point,
it completely from the K2.
TP1. Activate the frequency counter using
CAL FCTR
as
before.
Select 80 meters, and set the VFO for about 4000 kHz.
You should now see a frequency counter reading in the 8 to 10
Connect a DMM (digital multimeter) to the left end of resistor
MHz range. It may or may not be stable at this time (i.e., the
R30 (near the center of the synthesizer area of the RF board) and
frequency may be changing). If the reading is 0000 kHz or is
ground. Use a small alligator clip to ensure a good connection.
(You
changing rapidly, you probably don’t have the counter cable
connected to the VCO test point. If the reading is fairly stable
but
can also use the built-in voltmeter to measure the VCO control
voltage. Refer to Voltmeter Probe Assembly in Part I.)
not between 8 and 10 MHz, refer to Troubleshooting.
i
It is possible to damage the slugs in slug-tuned inductors if
Tap
MENU
to exit
CALFCTR
.
you use a metal tool or if you tune the slug too far in or out. The
tuning tool provided will not damage the slugs.
Using the wide end of the plastic tuning tool, adjust the slug in
inductor L30 until the voltage at R30 reads 6.0 V. If the
voltmeter
reading does not change at all as you tune L30 through its full
range, refer to Troubleshooting. If the voltage changes but you
cannot get to 6.0 V, you have probably wound the VCO inductor
(T5) incorrectly or have installed the wrong value at L30 or C72.
Set the VFO for approximately 3500 kHz.
Measure and write down the VCO control voltage at this
frequency in Table 6-1 (using pencil).
For each remaining band, set the VFO to the low and high
frequencies listed in Table 6-1 and write down the VCO control
voltages.
(You can tune quickly to the approximate frequencies in
2