User's Manual

300-Watt Digital UHF Transmitter Chapter 2, System Description
DT830A, Rev. 1 2-3
of the (A2) AC distribution panel. The AC
distribution panel contains four circuit
breakers, six in the upgradeable version,
which supply the AC to the rest of the
transmitter.
The input AC from TB1 is connected to
(CB1) the main AC circuit breaker (40
amps for DT830A and 80 amps for the
upgradeable version) which distributes
the 220 VAC to the terminal block (TB2).
TB2 has three MOVs mounted to the
terminal block: one is connected from
each leg of the input AC to ground and
the other one is connected across the
two legs.
The input AC is wired from TB2 through
three circuit breakers, CB2, CB3 and
CB4, CB5 and CB6 are used in the
upgradeable version, to the rest of the
transmitter. CB2 (10 amps) supplies the
AC voltage to the IEC outlet strip (A1)
into which the UHF exciter and any other
optional accessories are connected. CB3
(20 amps) supplies AC through J5 to (A6)
the UHF amplifier tray. CB4 (20 amps)
supplies AC through J6 to (A7) the UHF
amplifier tray. In the upgradeable
version, CB5 (20 amps) supplies AC
through J6 to (A8) the UHF amplifier tray
and CB6 (20 amps) supplies AC through
J6 to (A9) UHF amplifier tray. .When the
UHF exciter circuit breaker is switched
on, +12 VDC is supplied to the UHF
amplifier tray for the operation of the
LED status indicators in the tray.
2.2 Control and Status
Control and status indications of the
transmitter are provided by the meters
and LED indicators on the front panel of
the UHF exciter. The switches and LED
indicators are part of the transmitter
control board (1265-1311) which is
mounted so that the switches and the
LEDs can be operated or viewed from the
front panel of the UHF exciter. Switch S1
is an Operate/Standby switch that
controls the output of the transmitter by
providing the Enables, when in Operate,
needed to turn on the switching power
supplies in the two or four UHF amplifier
trays. In Operate, the green LED DS2 is
on and in Standby the amber LED DS1 is
on.
If the transmitter does not switch to
Operate when S1 is switched to Operate,
check that a dummy jumper plug, with a
jumper between pins 23 and 24, is
connected to jack J11 on the rear of the
UHF exciter tray or with a jumper
between pins 21 and 22 on jack J9 on
(A17) the (optional) input and remote
interface panel. This jumper provides the
interlock needed for the transmitter to
operate. If the interlock is present, the
green LED DS5 on the transmitter control
board should be lit. The front panel of the
UHF exciter also has an LED for VSWR
cutback (amber LED DS7).
2.2.1 (A19) 8-VSB Digital Modulator (1075164; Appendix C)
Table 2-2. Digital Modulator Display
DISPLAY FUNCTION
LCD
Provides a three-line readout of the internal
functions, external inputs, and status. See
Chapter 4, Detailed Alignment Procedures,
for a listing of display parameters.
The front panel has three pushbuttons for the control of the external and internal
functions.