AR 10036390, Руководство по эксплуатации и обслуживанию

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Model 800A3B
Rev D 32
3.5 FAULT DETECTION CIRCUITS
This section describes the function and theory of the Model 800A3B’s fault detection circuits. All fault-
signalling circuits are wired directly to the control panel for processing.
Detected fault signals are recorded in temporary (volatile) memory before the amplifier control circuits act to
protect the amplifier, sometimes resulting in RF inhibit or shut down. In some cases, inputs are read multiple
times to prevent a transient signal from causing an unwarranted action. Note that after a fault condition has
been invoked, the circuit breaker CB1 must be left on to keep the temporary memory active, so that all faults
can be manually recorded for diagnostic purposes. Faults may be recorded by the host system if the host
software is written to respond to fault conditions. Fault conditions may be queried at any time during normal
operation of the amplifier. When there are multiple faults, the display can be scrolled to view all of them.
3.5.1 Thermal Faults
Each of the 200 watt modules contains thermal sensor switches. In the case of a thermal fault, the line will go
high. The control panel displays the module designator and TH , and the main power supplies will be
inhibited to allow the modules to cool down.
3.5.2 Current Faults
Detailed theory of operation of the RF PA module is covered in Section 3.2.3. Parts dealing with faults are
explained here.
Refer to schematic diagram 10021041, 200 Watt Module . There are two possible faults that will signal the
control system. They are Over-current (OC), Under-current (UC) faults.
3.5.2.1 Over-current
On each 200 watt module, a current-sensing IC (U5) delivers an output voltage which is proportional to the
current being drawn. This voltage is compared to an adjustable reference voltage (R20) by an op-amp (U3A).
If U5’s output voltage exceeds the reference voltage, U3A’s output goes high to indicate that too much
current is being drawn. This causes the control panel to display the module designator and OC , as well as
inhibiting the main power supplies.
3.5.2.2 Under-current
Each 200 watt module has an op-amp which compares U5’s output voltage to an adjustable reference voltage
(R25) such that it detects an undercurrent condition. If U5’s output voltage drops below the reference
voltage, U3B’s output goes high to indicate that too little current is being drawn. This causes the control
panel to display the module designator and UC , as well as inhibiting the RF signal.
3.5.3 Power Supply Faults
The main power supplies are monitored internally. If a supply fails to produce DC voltage within its
specification, a logic signal will signal the fault board, resulting in an amplifier shut down. The power supply
faults and inhibit signals are routed to the A12 Control Panel. The fault signal is a logic high (+5VDC) when
all is well, switching to a logic low if a fault occurs.