2
6
30
sample from the Directional Coupler (DC1) is supplied to the FORWARD SAMPLE input (J1) and
the REFLECTED SAMPLE input (J2) of the detector. The si gnals are passed through resistive
attenuators R1/R2/R3, R9/R10/R11 and coupling capacitors C1, C7 to RMS detectors U1, U3. At
pin 7, U1 and U3 output the video component of the incoming UHF visual carriers while C3 and
C9 roll off the aural energy contained in each signal. The amplitude of the video is then doubled
using op-amps U2 and U4 and sent to peak detectors CR1/CR2 via pins 1 and 2 of jumpers JP1
and JP2. (Pins 2 and 3 of JP1 and JP2 are utilized for average digital power detection only.)
Capacitors C4/C10 and resistors R7/R15 filter the peak video component from diodes CR1/CR2
and each dc voltage is sent to unity gain buffers U2/U4. The dc levels at pin 7 of U2 and U4 are
now proportional to the peak forward or reflected power of the respective visual signals entering
the Metering Detector. These voltages will be delivered to the Control/Monitor board (A5PC1) to
provide FWD and REFL readings on the RF POWER meter mounted on the Control/Metering
panel (A5).
2.5
CONTROL/METERING PANEL:
Interconnection Diagram 40400003/Rev 52
t
A5
The Control/Metering panel displays various fault indicators and output power metering for the
TTU500FA Transmitter. The panel is located at the top front of the transmitter cabinet and
includes the Control/Monitor board (PC1) and a ±5V/±15V Power Supply (PS1), both mounted on
the rear of the panel.
2.5a
Control/Monitor Board:
Schematic Diagram 40400045/Rev 55
t
A5PC1
The Control/Monitor board, mounted on the rear side of the Control/Metering panel (A5) is the
control center for the TTU500FA Transmitter. All local and remote monitoring signals, control
voltages and interlock circuits are routed to their proper destination through this circuit board. Also,
the transmitter’s forward and reflected output power metering is controlled and displayed on this
board. Each multipin connector on the Control/Monitor is dedicated to an individual drawer or
assembly as described below.
500W Power Amplifier Interface (A3J3)
Jack – Pin #
Function
J1 – 5
PWR AMPLIFIER FAULT: This voltage is brought in from the Amplifier Status
Interface board located in the 500 Watt Amplifier drawer A3 through A3PC1J1-4
and A3J3-5, indicating that one of the 300W Amplifier (A3A1/A3A2) assemblies
has had an output transistor failure. Under normal operation this voltage will be
high forcing a high from U1A-3 which forward biases Q5, lighting AMPLIFIER
STATUS indicator DS1. In case of a transistor failure in drawer A3, this line will
go low driving U1A-3 low to turn off indicator DS1, but also causing AND gates
U1C, U2D and U1D to send a low to J3-1, the AMP STATUS output. This low
signal is forwarded to the Exciter drawer at A2J4-1 and on to the IF/Converter
Output AGC Control line (PC1J6-10) disabling the IF output AGC circuit so that
the transmitter continues to operate at reduced power.
