AR 10036484, Operating And Service Manual, Page: 48 / 58

Model 3000W1000B
32 Rev A
Voltage comparator U1 senses the presence of the –8 VDC. The output of U1 is high if the –8V supply is
–5.5 or less. The output of U1 pulls low when the –8 volts is present turning on Mosfet Q2 which supplies
the DC voltages to the drain of Q1.
The current through Q1 is monitored by U2. The output of U2 is fed to an op amp (U5) which has a
reference voltage on the non-inverting input and it compares the output of U2 to the reference voltage and
generates an error signal to vary the gate voltage of the RF transistor Q1 which controls the drain current.
U3 is a positive 5V regulator. It supplies DC to the current sense circuit, U2, the op amp, U5, and the fault
detection circuit, U6. SW1 is a thermal switch. It closes at a heat sink temperature of approximately 70
˚
to
protect the module in the event of an over-temperature condition.
3.3.4 Power Supplies, 500 Watt Power Amplifiers (PS1 and PS2)
Power supply PS2 supplies a +5VDC housekeeping supply for the control system assemblies A1 Switch
Breakout Assembly and A3 Fiber Optic interface for the system control.
PS2 also su24 VDC at 10 amps, +12 VDC at 13 amps, -12 VDC at 5 amps. PS2 is a switching
supply that automatically sets the AC input circuits to the correct connections for the line voltage 90-264
VAC input ranges 47-440 Hz.
The +24 VDC at 10.0 amp power supply is fed to the fans B1 and B2. The +12 VDC is fed to the A3
overdrive sense board.
The –12 V at 5 amps power supply is fed to the A7-A14 final modules to provide gate voltage for these
modules.
PS1 su23 VDC at 60 amps. PS1 is a switching power supply that automatically sets the AC input
circuits to the correct connections for the line voltage 120-240 VAC, 50-60 Hz.
PS1 su23 VDC to amplifiers A7-A14 to provide the drain voltage for these amplifiers.
3.4 TWELVE-WAY COMBINER
The 12-way combiner has impedance-matching. When the outputs of the 48 final amplifiers are fed to the
four 12-way combiners, the combined output will be approximately 10.8 dB above the output of a single final
amplifier.
3.5 A15 TWO-WAY COMBINER/DUAL DIRECTIONAL COUPLER
The 70 dB dual directional coupler is connected to the output of the 4-way combiner. The coupler monitors
the forward and reflected power.