AR 10044005, Operating And Service Manual

Page: 59 / 72

Model 5000A225A
Rev B 45
3.5.2 Current Faults
Refer to schematic diagram 10038146, 500 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 500 watt module, a current-sensing IC delivers an output voltage which is proportional to the current
being drawn. This voltage is compared to an adjustable reference voltage by an op-amp. If the output voltage
exceeds the reference voltage, the op amp’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 500 watt module has an op-amp which compares the current sense output voltage to an adjustable
reference voltage such that it detects an undercurrent condition. If the output voltage drops below the
reference voltage, the op amp’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 in the DCU and MPA’s 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 instant shut down.
The power supply faults and inhibit signals are routed to the Control Panel. The fault signal is a logic high
(+5VDC) when all is well, switching to a logic low if a fault occurs.
3.5.4 ALC Fault
An ALC fault is invoked whenever the forward or reverse power limit controls do not function, causing the
RF power to exceed one of the preset limits. The ALC fault is a logic low when invoked. The logic low from
the ALC board signals the digital control panel, which, in turn, disables the RF output by inhibiting the main
supply, PS1.
3.5.5 Interlocks
The Model 5000A225A Driver has two interlocks that are wired to the rear panel Safety Interlock connector.
The interlocks are separate circuits. Both interlocks require normally closed external circuits to allow the
amplifier to function.
3.5.5.1 Inhibit Interlock
For interlock applications where the amplifier is not required to shut down totally (AC Off), this interlock
circuit inhibits RF amplification by disabling the preamp in the DCU and power supplies and forcing the
amplifier into the Standby (RF Off) condition. The inhibit interlock is wired to the rear panel Interlock
connector pins 1 and 8. A closed circuit from Interlock connector pin 1 to pin 8 is required for normal
operation. Opening the connection will inhibit the Driver and display
Interlock on the front panel. When the