10
1-5-3-1 VFO TEST AND ALIGNMENT
SETUP:
Connect frequency counter to the switch side of C17 using a 10x scope probe. Preset C29 to the center of its
tuning range. Adjust the CAL RESET to center of its rotation.
Turn the OPERATION switch to MOX.
Turn the FUNCTION switch to AM mode.
Allow 30 minutes warm-up/stabilize time.
INITIAL PRESET.
Tune the main tuning dial to 300.
Adjust L4 for a reading of 4.550MHz on the frequency counter.
FINAL TRACKING ALIGNMENT.
Tune the main tuning to 100 and adjust C29 for 4.750MHz on the counter.
Tune the main tuning to 400 and adjust L4 for 4.450MHz on the counter.
NOTE: These two adjustments interact, you may have to go back and forth, under or over correction at
one or the other end to get both ends correct.
FINAL TRACKING CHECK
MAIN TUNING
FREQUENCY
0
0
4.850MHz
100
4.750MHz
200
4.650MHz
300
4.550MHz
400
4.450MHz
500
4.350MHz
Move the scope probe from the frequency counter to the scope
Set the main tuning to 250.
Adjust L2 for max signal. This signal should exceed 0.500 vpp.
Turn main tuning from 250 to 500 then to 0. The signal should not drop more than 0.075 volts at either end.
This completes the VFO tests and adjustments.
VFO VOLTAGE CHART
OPERATION FUNCTION
V10
PIN 1
PIN 2
PIN 3
PIN 6
PIN 7
PIN 8
PIN 9
MOX
AM
141vdc
0
86
141*
0
4
0
*Measured at junction of L2 & R24
