MFJ-9420 Installation Manual
20-Meter SSB Travel Radio
3. RADIO DOES NOT TRANSMIT OR KEYS ERRATICALLY
Is microphone and connector okay?
4. ERRATIC TRANSMIT
Is SWR high (above 3:1)?
Is power source voltage low or "soft" under load?
5. AGC IS INEFFECTIVE OR S-METER IS NOT ZEROED
Is Regulator okay (10.0 V on TP1)?
Is AGC okay (4.3 on TP2?)
If TP1, TP2 is okay and AGC works, rezero meter via R51.
6. RADIO DRIFTS IN FREQUENCY
Is radio sitting in Sun, on hot surface, in cold draft?
Was radio moved from extreme cold to warm (condensation)?
If you suspect condensation, allow radio to fully dry out.
7. POOR CARRIER SUPPRESSION
Was radio moved from extreme cold to warm (condensation)?
Was radio exposed to rough handling or shock?
To null, unplug mic and ground pin 3 to key radio. Adjust R36 and T3 for minimum carrier (monitor using a
second receiver).
8. LOW TRANSMIT AUDIO:
Is the mic a 600 ohm dynamic type?
Is the MIC GAIN set too low?
9. NOISE ON TRANSMIT AUDIO:
Is MIC GAIN set too high in a noisy room?
Is mic next to a power transformer or motor?
If these checks don't uncover the problem, or if you do not feel qualified to make the prescribed adjustments, please
call us for help at 800-647-TECH (800-647-8324).
FIELD ALIGNMENT PROCEDURES FOR THE MFJ-9420 TRANSCEIVER
SPECIAL TOOLS, PARTS, TEST EQUIPMENT:
AC Power Supply, 13.8 Volts @ 2 Amps
Voltmeter
Non-inductive Alignment Tool kit
Frequency Counter
Wattmeter with 50 Ohm Resistive Dummy Load
14 MHZ Signal Generator or other weak signal source
General Coverage Receiver with digital readout
INITIAL TEST SET UP:
A. Remove transceiver cover.
B. Connect 13.8 Volts Power Supply to Power Jack.
C. Connect Microphone.
D. Turn on unit.
VOLTAGE CHECKS AND ADJUSTMENTS: (use voltmeter)
A. VOLTAGE REGULATOR: Set R64 for 10.0 V at TP1.
B. RECEIVER AGC: Set R6 for 4.3 Volts at TP2.
VFO CALIBRATION:
A. Tune the VFO dial to 14.250 MHz (mid band).
B. Connect counter probe to U7 pin 6
C. Adjust L3 for 4.255 MHz readout.
