User's Manual

350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-6
Table 2-8: VHF Amplifier Tray Fault Indicators
INDICATOR DESCRIPTION
DS1
Overdrive
Indicates that the level of drive is too high. The protection
circuit will limit the drive level to the set threshold. The fault
is generated on the overdrive protection board.
DS2
Enable
Indicates that the Enable supplied by the driver/amplifier
chassis assembly is present
DS3
Module Status
Indicates that the forward power sample level is lower than
the set reference level
DS4
VSWR Cutback
Indicates that the reflected level of the tray has increased
above 20%; this will automatically cut back the output power
of the tray. The fault is generated on the AGC control board.
DS5
Overtemperature
Indicates that the temperature of (A13, A14 or A15) one of
the thermal switches is above 175° F. When this fault
occurs, the Enable to the switching power supply is
immediately removed.
2.4: Control and Status
The control and status of the
exciter/amplifier chassis assembly is found
by operating the front panel display screen
on the assembly. Detailed information on
the use of the screen is found in Chapter 3
of this manual.
2.4.1: Front Panel Display Screen
A 4 x 20 display located on the front of
the Control & Monitoring/Power Supply
Module is used in the transmitter for
control of the operation and display of
the operating parameters of the
transmitter.
2.5: System Operation
When the transmitter is in operate, as set
by the menu screen located on the
Control & Monitoring Module, the +32
VDC stage of the Power Supply in the
Control & Monitoring Module is enabled,
the operate indicator on the front panel is
lit and the DC OK on the front panel
should also be green. The enable and DC
OK indicators on the PA Module will also
be turned to green.
When the transmitter is in standby, the
IF Processor will be disabled and the
mute indicator on the front panel will be
red. Also, the +32 VDC stage of the
Power Supply in the Control & Monitoring
Module is disabled, the operate indicator
on the front panel will be extinguished
and the DC OK on the front panel should
remain green. The enable and indicator
on the PA Module is also extinguished.
If the transmitter does not switch to
Operate when the operate menu is
switched to Operate, check that all faults
are cleared and that the remote control
terminal block stand-by signal is not
active. Also check that a jumper or
external closed interlock is connected
from J30-5 to J30-15 on the rear of the
exciter/deriver chassis assembly.
2.5.1: Principles of Operation
Operating Modes
This transmitter is either operating or in
standby mode. The sections below
discuss the characteristics of each of
these modes.
Operate Mode
Operate mode is the normal mode for
the transmitter when it is providing RF
power output. To provide RF power to
the output, the transmitter will not be in
mute. Mute is a special case of the
operate mode where the power supply's
32 VDC section is enabled but there is
no RF output power, because of a fault
condition that causes the firmware to