Assembly Instructions Chapter 4

10-kW UHF Transmitter with Chapter 4, Circuit
Feedforward Drive Descriptions
840A, Rev. 0 4-36
this is applied to DS15, the Cathode I
Fault LED on the board, causing it to
light. Because of the high on its input at
U11-3, the output of U11 at pin 1 goes
high and resets clock IC U9. The Q1 and
Q0 outputs of U9 go low during reset,
then back to high, and are applied to
U14, whose output will be high when
both inputs are high. The high is
connected to U14-2 and, when U14-1
goes high, the output at U14-3 also goes
high and resets the three R-S latches
that make up U16. The transmitter will
reset three times, to confirm that a fault
has actually occurred, and counter IC
U15 will count each time a high is applied
to pin 1. After the third fault, the U15 IC
will latch and produce a low at U7-15
that connects to the Three Fault LED
DS11, causing it to light.
After the problem that caused the fault is
corrected, the fault circuit is reset by
switching the front panel-mounted reset
switch S9. This places a low at J6-9 on
the board that is inverted by U18. The
high is connected to pin 7, the R1 reset
input of one of four quad R-S latches that
make up U16, and to U12-8. The high at
pin 7 of U16 resets the temperature fault
circuit. The high at U12-8 causes the
output of U12 at pin 10 to go high and
connects to the reset input at pin 7 of
U15. U15 then resets the front panel-
mounted fault indicator and the fault
circuits associated with U16. The three-
fault indicator and the other fault
indicators that are lit on the board are
reset by switching S1.
The +12 VDC needed for the operation of
the board enters at jack J1, pin 1. C1, C2
and C3, and L1 are for the filtering and
isolation of the +12 VDC before it is
applied to the rest of the board.
4.2.5.2 Transmitter Control Board (1137-
1003; Appendix B)
The transmitter control board in the
metering control panel provides the
system control functions for the
transmitter. The board supplies the
interlock to the exciter tray and also
provides the outputs to the function
indicator LEDs on the front panel of the
metering control panel. The transmitter
control board will switch the transmitter
to Standby upon the loss of the video
input from the modulator or from the
receiver tray, if present, when the
transmitter is in Automatic.
When the Operate/Standby switch on the
front panel of the metering control panel
is switched to Operate (J11-8 low), and
the Normal/Exciter Test switch is in
Normal (K4 energized), K3 energizes and
applies a low to inverter U8F, causing its
output to go high. The low from K3 also
biases off Q23 and Q24; this removes the
Standby commands. The high output of
U8F, at pin 15, forward biases Q18 to
Q22 and applies the Operate commands
to the control logic board. The low is also
applied through diode CR12 to pin 11 of
inverter U8E, causing its output to go
high. The high forward biases Q26 and
Q27; this causes the drains to go low and
lights DS14, the front panel Normal LED
connected to J14, pins 8 and 6. The high
output of U8E also connects to pin 5, the
input to inverter U8B, causing the output
at pin 4 to go low. The low is applied to
Q28 to Q33, biasing them off and
removing the exciter test functions.
When the Operate/Standby switch on the
front panel of the metering control panel
is switched to Standby (J11-2 low), and
the Normal/Exciter Test switch is in
Normal (K4 energized), K3 de-energizes
and applies a high to inverter U8F, pin
14, and also to Q23 and Q24. As a result,
Q23 and Q24 are forward biased; this
produces a low at J12, pin 3, and lights
DS2, the front panel-mounted Standby
LED. The high on inverter U8F, pin 14,
causes the output at pin 15 to go low.
The low reverse biases Q18 to Q22 and
removes the Operate commands to the
control logic board and the amplifier
trays. The high from K3 is also applied to
diode CR12, causing it to reverse bias.