Model 2500A225C
44
Rev A
The current through Q1 is monitored by U1. The output of U1 is fed to an op amp (U3) which has a reference
voltage on the non-inverting input. U3 compares the output of U1 to the reference voltage and generates an
error signal. This error signal varies the gate voltages of Q1 which in turn controls Q1’s current draw.
U5 is a comparator that monitors the output of U1 and generates a fault signal if the drain current varies outside
normal operating conditions. It also monitors the module temperature via a thermistor (R31) and generates a
fault signal if the module heatsink exceeds approximately 80
o
C
3.2.5
A13 Eight-Way Combiner
The Eight-Way Combiner operates in 180-degree configuration with a broadband range of .01-225 MHz. The
combiner is designed to tolerate loss of input signals at full power.
3.2.6
A24 Bi-Directional Coupler
The A24 Bi-Directional Coupler takes a sampling of the forward and reverse RF output signal for use in the
automatic level control and display circuitry. The RF coupling of the forward and reverse coupled ports is
approximately 63 dB.
3.2.7
A23 Detector
The A23 Detector converts the RF signals from the bi-directional coupler to a DC voltage for use in the
automatic leveling, sample ports, and display circuitry.
3.3 POWER SUPPLIES
The Model 2500A225C contains seven switching power supplies. The input voltage range to the power supply
is 200–240 VAC, 50/60Hz. The AC input power is approximately 8500 watts.
PS1 is a multiple output supply. PS1 has a +5V, standby supply for the A14 control panel, the A15 remote
interface board used for the remote interfaces, the -15V supplied to the A1 preamp, the A2 driver module and
the A5-A12
final modules. The +15V is supplied to the A5 through A12 final modules, the A23 dual detector
assembly, and the A17 interlock isolation assembly.
PS2 su40V to A1 preamp/driver module and the A22 regulator assembly.
PS3su24 VDC to the module shrouds cooling fans. PS3 also powers the A13 combiner, and A2 splitter
fans.
PS4 through PS6 are 2500W, 1U power supplies which 47 V to the A5 through A12 final modules.
Primary AC circuit protection is provided by the (CB1) circuit breaker located on the rear panel.
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