MFJ-939 Plug&Play IntelliTuner Automatic Antenna Tuner
Instruction Manual
2006-2015 MFJ Enterprises, Inc.
30
and the green LED will blink. If there is a problem, message “PD FAIL” will be sent as Morse
code repetitively and the red LED will blink.
9.
Turn the power off.
Relay Test
WARNING:
Turn off the transmitter power or disconnect the transmitter before
performing this test; otherwise, damage to the tuner can result.
To test the relays and their control circuitry;
1.
Turn off the power to the tuner.
2.
Press and hold
only
the [ALT] button while turning the power on. Both LEDs will blink until the
button is released.
3.
Within four seconds of releasing [ALT], press the [TUNE] button five times.
4.
After releasing [TUNE] for four seconds, beep once and the Relay Test routine is initiated.
5.
Press the [TUNE] button to engage the relay and the red LED will turn on. Release the [TUNE]
button to disengage the relay and the red LED will turn off. Listen for relay clicks.
6.
There are 18 relays in the tuner, yet there are 19 test positions. The second relay tested (K2) is not
used in this unit. There will be no relay click for K2. Press the [ALT] button to test the next relay.
The green LED will illuminate until the [ALT] button is released.
7.
Repeat Steps 5 and 6 to test all 18 relays (in the order of relay K1 to K19, K2 is not used in this
unit).
8.
After releasing [ALT] on the 19
th
test position, the unit will beep three times and resume normal
operation.
Frequency Counter Calibration
To calibrate the frequency counter, you will need a transmitter, a 50-ohm dummy load, two 50-ohm SO-
239 coax cables, a Phillips screwdriver, and a tuning tool or small flat blade screwdriver.
WARNING:
Do not touch anything inside the tuner during operation! Serious, painful
RF burns can result.
WARNING:
Never operate the MFJ-939 with its cover removed; dangerous voltages
and currents can be present during operation. Never exceed tuner
specifications.
1.
Turn off the power to the transmitter and the tuner.
2.
Remove the cover from the tuner (10 screws) with a Phillips screwdriver.
3.
Connect the 50-ohm dummy load to the ANTENNA connector; connect the transmitter to the
TRANSMITTER connector on the tuner.
4.
Turn on the power to the transmitter. Set and lock the frequency to
exactly
29.000 MHz.
5.
Press and hold
only
the [ALT] button while turning the power on. Both LEDs will blink until the
button is released.
6.
Within four seconds of releasing [ALT], press the [TUNE] button six times.
7.
After releasing [TUNE] for four seconds, the green LED lights up and the Frequency Counter
Calibration is initiated.
8.
Key the transmitter to output about 10 watts and adjust trimmer capacitor VC3 (located next to
the big integrated circuit on the front side of the front panel circuit board) until both LEDs are
