Harris DX 25U, Техническое руководство

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former T10 may need to be used to increase, or “BOOST”,
the amplitude of the drive. This is achieved by attaching
reversing the lead connections on the transformer winding
to the combiner bar and the combiner bar cover. The length
of the Driver Tuning strap 1L5 may need to be changed to
achieve resonance if T10 is used.
p. The optimum combination is:
1. Driver Current of 22 Amps or less
2. All Driver Modules active (D1-D5 and D9-D14)
3. The Drive Regulator operating with DRIVER D8A
voltage b40 and +95 VDC
4. BUCK/BOOST transformer T10 out of circuit or in the
“BOOST” mode
q. When the optimum drive level is obtained, refer to the
Driver Encoder/Temp Sense section for the AUTO Driver
circuit adjustment procedure.
5.7.6.1
Closed LOOP Adjustment
a. When the RF drive level has been set at 24.0 Vp-p, note
the DRIVER D8A voltage.
b. Set the LOOP select switch S1 on the Driver Supply
Regulator to the Closed position.
c. Adjust Closed Loop adjustment R12, on the Driver Supply
Regulator, for the same reading on the DRIVER D8A
reading. The RF drive level should remain between 22.0
and 24.0 Vp-p. The LOOP select switch is normally left in
the Closed position for normal operation.
NOTE
MAKE SURE TO REINSTALL P1 ON THE ANALOG INPUT
BOARD IN THE NORMAL POSITION BEFORE PROCEEDING
WITH INITIAL TUNING AT LOW POWER.
d. Remove jumper between TP8 and ground on the LED
Board. This activates the Underdrive Overload circuitry.
5.7.6.2 Underdrive/Overdrive overloads
If it is desired to set the Underdrive and Overdrive overloads refer
to the “Underdrive and Overdrive Overload Setting” paragraphs
in the LED Board adjustment procedure.
5.7.6.3
RF Drive Phase
Even though not necessary for a frequency change, the RF drive
phasing and Drain Phasing can be checked. For Drive Level and
Phasing measurement procedures see “Measuring RF Drive
Phasing,” paragraph and “Measuring RF Amplifier Drain Phas-
ing,” paragraphs in SECTION VI, Troubleshooting.
5.7.7
Initial Tuning At Low Power
WARNING
ENSURE ALL PRIMARY AC POWER IS REMOVED FROM TRANS-
MITTER AND THAT A GROUNDING STICK HAS BEEN USED TO
DISCHARGE ANY RESIDUAL POTENTIAL WHERE POWER HAS
BEEN APPLIED BEFORE PERFORMING THE FOLLOWING
STEPS.
a. Remove the rear access panels from the Driver Compart-
ment and the left rear RF Amp Compartment and replace
the following PA Power Supply fuses:
1. A25: F1-F8
2. A24: F1-F9
3. F20: (on top of T1)
b. Apply primary AC power to the transmitter. Turn on the
low voltage at CB1 and CB2.
c. Verify that all LED’s on the ColorStat™ panel are illumi-
nated Green.
d. Verify that the transmitter is properly terminated into a
Dummy load.
e. Turn the PA TURN-OFF Switch on the Controller to the
OFF (up) position.
CAUTION
REMOVE JUMPER FROM THE LED BOARD A32 FOR PROPER
DRIVE SENSING BEFORE PROCEEDING.
f. Depress the LOW power button. The PA Power supply
should energize, but no RF output or PA current should be
indicated.
g. Connect a meter to measure between 0.0 and +3.0 VDC to
TP7 on the Analog input Board.
h. Press and hold the Fast Power Set switch S1 on the Con-
troller. While holding S1 down, press the LOWER button
on the front panel. The voltage at TP7 should quickly drop
to zero. The power output of the transmitter is now set to
zero.
i. Set the PA TURN-OFF switch to the ON (down) position.
j. Press the RAISE button. Power output should begin to
increase along with the PA current indication. Continue to
raise power until the power meter indicates 5.0 kW.
k. Change the Multimeter selection switch from PA +VDC
to FILTER NULL. Power meter selector switch should be
in FWD.
l. Adjust the TUNING control for maximum output as noted
on the front panel Power meter.
m. FILTER NULL and ANTENNA NULL may begin to rise.
Adjust the Antenna and bandpass filter null on the Output
Monitor if necessary. Refer to the adjustment procedure
for the Output Monitor in this section.
5.7.7.1
Modulated B-Check
a. Modulate the transmitter at 5.0 kW with a 100 Hz sine
wave at 100% modulation.
b. Connect a scope probe to TP6 or TP30 on the DC Regula-
tor. Displayed will be the Modulated B- waveform similar
to the one in Figure 5-7.
c. Set the scope for 1 volt per division, dc coupled and the 0.0
VDC line on the top graticule. The positive peak of the
waveform should be from -2.0 to -2.7 VDC. The negative
peak should occur between -3.0 and -4.5 VDC.
d. If the waveform is not within these tolerances then the
Modulated B-Adjustments should be set using the proce-
dure in the Analog Input Board and DC Regulator para-
graphs in this section.
DX-25U
5-18 888-2297-002 Rev. Z1: 06-02-00 Additional info to ECN 46105
WARNING: Disconnect primary power prior to servicing.