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J.2.4.

Power Output Calibration

Connect the transmitter into a load with

the capability of accurately measuring the
power output. This is best done with a cal-
orimetric dummy load, where the water
temperature rise is measured against a
known flow rate. A second choice is a
dummy load and an RF ammeter of known
accuracy.

Operate the transmitter at a convenient

power level within the capabilities of the
test setup.

Calibrate the Power Output meter to the

same reading as measured externally using
R85 on the Controller board.

J.3.

Overload Adjustment Procedures

J.3.1.

Power Supply Current Overload

Check the present Power Supply Current

reading against the value on the factory test
data sheet for the same operating condi-
tions. If the present reading is significantly
higher, it will be advisable to investigate the
cause before proceeding with the following
overload adjustment.

The overload threshold can be set to the

same value as recorded on the factory test
data sheet, or by checking the trip threshold
by modulating it with a tone according to
the following procedure.

For setting the overload under modulating

conditions, operate the transmitter at 110%
of its rated power output (5500 watts for
GATES FIVE, 2750 watts for a GATES
TWO, and 1100 watts for a GATES ONE).

Modulate with 20 Hz to 100%. Increase

the audio level 0.5dB (6%).

Adjust R11 counterclockwise until the

transmitter faults, then 1/3 of a turn clock-
wise from this trip point.

J.3.2.

Underdrive Fault

For the Underdrive fault, a comparison is

made between the RF Drive level reading
and a threshold which is a function of power
level. The RF Drive level reading is what is
adjusted during the alignment procedure.

The RF Drive level reading should always

be somewhat higher than the Underdrive
Set reading.

If you are replacing the Controller board,

and already know that the actual RF Drive
level is okay, you will only need to duplicate
your normal reading for High power.

A more in depth check of the overload

function requires verifying the correct RF
drive amplitude (26-32 Vpp) is present
across R13, R14, R23, R24, R33, R34, R43
and R44 for each PA module. For the pro-
cedure on checking the drive on the PA
module(s), refer to Section H.

After verifying the actual RF drive to be

in the normal range, modulate the transmit-
ter to 100% with 400 Hz at 110% power
output (5500 watts for GATES FIVE, 2750
watts for a GATES TWO, and 1100 watts
for a GATES ONE).

Adjust R143 clockwise until the transmit-

ter trips to the next lower power level and
displays the Underdrive fault. Then rotate
R143 counterclockwise from the trip point
about 2 turns.

J.3.3.

VSWR Detector

You may set the VSWR trip threshold

using the value recorded on the factory test
data sheets, or may use a more involved
process which actually causes the overload
circuit to operate.

With the transmitter on, and NO modula-

tion applied, set the LOW power control all
the way to zero power output.

Use a clip lead to short across R18 on the

Output Monitor board. This will cause the
VSWR detector to not be nulled when you
bring up RF power.

Gradually increase the power output, and

watch the VSWR Detector Null reading
come up from zero. Adjust R14 so that the
transmitter trips off when the VSWR Detec-
tor Null reading reaches 7.5 on the Mul-
timeter.

J.4.

Troubleshooting the Controller

Numerous components are duplicate

types in control, status, metering, and over-
load functions. This can be advantageous
in terms of isolating a problem and getting
back on the air in the event of a component
failure.

The Chart of Functions lists the IC types

used and their functions. Those designated
by an asterisk (*) are for status indications
or metering, and not necessary to the opera-
tion of the transmitter at any power level.
Therefore, any of these could be transferred
to a needed function where a failure oc-
curred if no replacement was immediately
available.

J.4.1.

Symptom: Will Not Respond To
An On Command

(None of the status LED’s on the power

level switches illuminate.)

Possible Causes:

J.4.1.1.

Controller Supply Failure

Check the status of the +/-12 volt indica-

tors. Measure the +/-12 volts on the Con-
troller board. Feel the regulators U32 and
U33. If one is hot, it probably means there
is a shorted component loading the supply
down on the Controller.

J.4.1.2.

Failed flip flop circuitry

Check the operation of U4, U5, and U6 or

replace them. Also check or replace NOR
gates U7, U8, U9, U10, U11, and U12. A
logic zero on the outputs of the NOR gates
will hold the flip flops in an OFF mode.

J.4.2.

Symptom: PDM Power Level Sig-
nal Cannot Be Controlled

Possible causes:
Check to see if there is a PDM Kill or

overload condition. Check or replace U19.

J.4.3.

Symptom: Multimeter Is Pinned
Far Left or Right

Check to see if it matters which position

the meter switch is in. If it does not, replace
U20 on the Controller. Otherwise, both U20
and U21 are suspect.

J.4.4.

Symptom: Some Remote Control
Functions Do Not Work

Possible causes:
Optical Isolator Failure. Failures in this

area would probably inhibit only those in-
puts with defective optical isolators. Ohm-
meter test the input side of U1, U2, and U3
on the Controller board. These should test
as diodes. Otherwise, measure across each
optical isolator input on the Controller to
see if a voltage is being applied as the
remote control circuits are activated.

U1*

ILQ-1

Remote LOW through
FOUR power level
control

U2*

ILQ-1

Remote FIVE, SIX, OFF,
and EXT KILL control

U3*

ILQ-1

Remote Raise, Lower,
and Indicator Reset

74C74

LOW and TWO power
selection flip flop

74C74