Harris DX 25U, Техническое руководство

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pr60 VDC for the Predriver and Binary Amplifiers and
is filtered by 10 mH choke L3 and capacitors C10 and C42.
4.4.8
Supply Current Meter, M2
The negative sides of the rectifier assemblies are tied to the PA
Power Supply current meter shunt SH1 in the Driver Compart-
ment. The total +230 VDC supply current returns to ground at
this point. The Supply Current meter (M2) on the transmitter
front panel is connected across the shunt.
The voltage across the shunt is proportional to supply current
and also goes to the supply current overload circuit on the LED
Board from the Switch Board/Meter Panel. The current overload
circuit also provides a remote supply current metering output.
Refer to SECTION Q, LED Board, for a description of the
supply current overload circuit.
4.4.9
Secondary Winding Fuses
The secondary winding of the PA Power Supply is protected by
fuses mounted on the top of transformer T1: 250 Amp fuses F1
through F12 protect the secondary windings from a short circuit
in the +230 VDC rectifier assemblies or output bus and 35 Amp
fuses F13, F14, and F15, protect the secondary windings for the
+115 VDC and +60 VDC supplies.
4.4.10
Supply Fuses
Two 25 Amp fuses, F20 and F21 mounted on top of transformer
T1, protect the +60 VDC supply to the Predriver and the Binary
RF amplifiers.
The +230 VDC supply is fed to the A24 and A25 Fuse Boards
where 16 individual 50 Amp fuses feed 5,100 uF filter capacitors
mounted near the Combiner Motherboards. Each capacitor sup-
plies filtering for eight RF amplifier modules.
The +115 VDC supply for the Driver and Binary RF amplifiers
is fed to the A25 Fuse Board. The +115 VDC Binary supply is
fused by 25 Amp fuse F9 and the +115 VDC Driver supply is
fused by 30 Amp fuse F10.
On each Fuse Board, a series diode and parallel resistor provide
a fast discharge path for the capacitor if a fuse opens.
4.4.11
Fan Motor Fuses
The fan motors B1 through B4 are fused separately by 1 Amp
cartridge fuses F11 through F13, F21 through F23, F31 through
F33 and F41 through F43. Fuses F17, F18, and F19 are 15 Amp
cartridge fuses and protect the wiring between the primary of
T1 and the fan motor fuses.
4.4.12
A24 and A25 Fuse Board Sample Circuits
Five +230 VDC sample circuits are located on the two fuse
boards. These five samples are routed to the LED Board, Analog
Input Board, and Driver Supply Regulator. The Analog Input
Board sample is located on the A25 Fuse Board and the other
four samples are located on the A24 Fuse Board.
4.4.12.1
Analog Input Sample
A DC power supply compensation signal for circuitry on the
Analog Input Board comes from R22, R23, R24, R27, and C3.
Refer to SECTION J, Analog Input Board, for the circuit de-
scription.
4.4.12.2
Driver Supply Regulator Sample
Parallel resistors R25-R26 from the +230 VDC supply are
collector load resistors for the Driver Supply Regulator Q2
circuit. Refer to SECTION E, Driver Supply Regulator, for the
circuit description.
4.4.12.3
Supply Fault Sample
An AC sample of power supply “ripple” for the power supply
protection circuit on the LED Board is provided by voltage
divider R14 and R15. Capacitors C1 and C2 block DC and form
an AC voltage divider. Transzorb CR11 provides overvoltage or
transient protection. Refer to SECTION Q, LED Board, for a
description of the Power Supply Protection circuit.
4.4.12.4 PA Supply VDC sample
Resistors R16, R17 and R18 form a voltage divided signal for
remote and local PA Supply VDC readings. The signal passes
through the LED Board and then to the Controller. A voltage
follower amplifier on the Controller provides outputs to the front
panel multimeter and to the External Interface for remote supply
voltage metering. Refer to SECTION P, Controller, for a de-
scription of the PA Supply VDC metering circuit.
4.4.12.5 PA Supply Overvoltage Sample
Resistors R19, R20 and R21 form a voltage divider for the
overvoltage circuit on the LED Board. Refer to SECTION Q,
LED Board, for a circuit description.
4.4.13
AC Power Protection Circuits
The following information highlights circuits that function as a
result of variations in AC line conditions.
4.4.14
Overvoltage and Undervoltage Protection
The “PA Power Supply” DC overvoltage protection on the LED
Board will shut the transmitter OFF in case of overvoltage
conditions. If high or low supply voltages to the Driver stage
results in excessive RF drive level changes, RF Overdrive or
Underdrive circuits on the LED Board also shut the transmitter
off.
4.4.15
Loss of Phase and “Brown-Out” Protection
Circuitry on the LED Board provides protection against loss of
phase or line imbalance (Brown-out). If either condition is
detected, a circuit will turn off the PA Power Supply and a
Supply Fault will be indicated on the ColorStat™ panel. Refer
to SECTION Q, LED Board, for a description of the Power
Supply Protection circuit.
4.5
Air System and Sensing Circuits
Refer to the DX-25U Cabinet Outline drawing, 839-7855-152,
and Overall schematic, 839-7855-151. Additional information
is also available in SECTION II, Installation/Initial Turn-On,
SECTION V, Maintenance, and SECTION S, Driver En-
coder/Temp Sense Board.
Section IV - Overall System Theory
Rev. AA: 8-9-00 888-2297-002 4-5
WARNING: Disconnect primary power prior to servicing.