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HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
149
is lit if an interlock occurs. Since this feature is not always used, J15 can be set to
disable this interlock.
5.6.1.2 Sheet 2
This sheet contains the cabinet ON/OFF logic, power supply control and fault detection.
ON/OFF commands are received from the main controller through J2, but if the
external connection is removed from J2 the cabinet can be controlled locally with S2
and S3.
An ON command sets TX ON/OFF Latch U20, sending an AC-CTRL* signal through
U25-1 and U25-3 to turn on the cabinet AC contactor. A cabinet door fault causes a
LOW on pin 2 of U25, stopping the contactor from turning ON.
The contactor applies power to the cabinet blower and to the 50 Volt power supplies.
PS1 and PS2 also receive ON commands from U19-3 and U19-5, but the ON
commands are delayed until U11-12 receives an AIR ON* signal indicating proper
cooling air pressure.
Each power supply receives a control command turning it ON and OFF, and returns a
PS OK signal when it is operating and has not faulted. The PS OK signals are monitored
by U18-6 and U18-8, indicated by PS Fault LED'S DS3 and D54. Each will show a
FAULT condition if the TX ON/OFF LATCH is set to ON and it's power supply is not
returning a PS OK signal. The PS FAULT lights will light briefly each time the PA is
operated to ON, until the power supplies come on, and then will light only if the supply
faults.
A power supply can be reset with the same ON command used to reset the modules.
The TXD and TXD* signals processed by the TX ON/OFF LATCH are used elsewhere
on the board to control the modules and other logic. The ON command sent to the TX
ON/OFF LATCH is also sent to U22, the STSET ONESHOT. U22 produces a 700ms
one-shot pulse, STSET and STSET*, which are used to reset PA modules and other
equipment when the ON button is pressed while the transmitter is operating.
5.6.1.3 Sheets 3 and 4
Receive MODF (Module Fault) status from, each of the 17 PA modules in the cabinet,
and also Cabinet Interlock if used. The status of each is read back to the Monitor board,
arid the MODF signals are also used to route reset signals to the proper modules.
5.6.1.4 Sheet 5
This sheet contains 6 additional RF peak detectors functionally identical to the detectors
on the main controller. These added detectors are used as needed to detect added
samples in larger transmitters.