MFJ-991 / MFJ-994 IntelliTuner Automatic Antenna Tuners
Instruction Manual
©
2004 MFJ Enterprises, Inc.
18
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, press and hold the [C-DN] button while turning the power
on. Both meter needles will bounce. Release the button. The relays are tested in groups of four as shown
in the table below. The [C-UP], [L-UP], [C-DN] and [L-DN] buttons are used to toggle each relay in
each group of four. Press button to engage the relay and release it to disengage the relay. Listen for relay
clicks. Press the [TUNE] button to proceed to the next group of four relays. There are 18 relays in the
tuner. Repeat the above procedure to test all the relays. Normal operation is resumed after this test. The
reflected power needle indicates which group of relays is being checked as follows:
Reflected Needle
[C-UP]
[L-UP]
[C-DN]
[L-DN]
1-watt mark
1
Not used
3
4
2-watt
mark
5 6 7 8
3-watt mark
9
10
11
12
4-watt mark
13
14
15
16
5-watt mark
17
18
19
Not used
Since there are no relays #2 and #20, pressing the [L-UP] button in the first group and the last button [L-
DN] in the last group will not produce a click.
Wattmeter Calibration
To calibrate the wattmeter, you will need a Phillips screwdriver and a tuning tool or small flat blade
screwdriver.
WARNING: Never operate the MFJ-991/4 with its cover removed; dangerous voltages and
currents can be present during operation. Never exceed tuner specifications.
Note: The trimmers involved in this calibration are located on the circuit board behind the front
panel; do not confuse these with the SWR bridge trimmers.
1. Turn off the power to the tuner and the transmitter.
2. Remove the cover from the tuner (12 screws) with a Phillips screwdriver.
3. Press
and
hold
both
the [TUNE] and [C-UP] buttons while turning the power on. Both meter needles
will bounce. Release the buttons.
4. The forward needle will go up. Use a small flat blade screwdriver and adjust the FWD trimpot R75,
located behind the display, to set the forward power needle to the 100 watts mark.
5. Press [TUNE] to calibrate the reflected power needle. The forward needle will drop to zero and the
reflected needle will go up.
6. Adjust the REF trimpot R76, located behind the display, to set the reflected power needle to the 20
watts mark.
7. Press [TUNE] to resume normal operation.
8. Turn off the tuner power and secure the cover back onto the tuner.
Summary of Contents for IntelliTuner -991
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