User's Manual

Innovator CU0TD-1/CU0RD-1 – CU4TD/CU4RD ATSC Board Descriptions
Transmitter/Regenerative Translator
Instruction Manual, Rev. 2 119
(A8 & A9) One, two & three pallet Amplifier Drawer Power Supplies
The 230VAC, needed to operate the drawer, connects through the AC power cord at J3,
the power entry module located on the rear panel of the drawer. The AC lines are
connected to a terminal block TB1 to which the circuit breaker(s) connect. In a N+1 one
pallet amplifier drawer and all multiple pallet amplifier drawers, there are two On/Off
20A/250VAC circuit breakers that are mounted on the back panel of the drawer on either
side of J3 the AC input jack. With the circuit breakers switched On, the AC is distributed
to the two (A8 and A9) DC power supplies. In a standard one pallet amplifier drawer
one 20 Amp circuit breaker CB1 connects the AC to the (A8) DC power supply. TB1 has
three varistors (VR1-VR3) connected across the AC input lines for surge and over
voltage protection. The AC input from TB1 also connects to through 2 amp fuses to the
two fans (A11 & A12) mounted in the drawer. Both fans will run immediately when AC
is applied to the drawer.
The +5VDC for the operation of the amplifier control board in the drawer is generated by
the (A8 & A9) power supplies at J1-9 on each power supply. The +5VDC from the (A8)
power supply connects to J4-8 and the +5VDC from the (A9) power supply connects to
J5-8 on the control board. The +5VDC is produced when AC is connected to the drawer
and the CB1 and/or the CB2 circuit breakers are turned On. Either or both power
supplies provides the +5VDC for use by the control board.
The +48VDC needed by the amplifier modules on the heatsink assembly is generated by
the (A8 & A9) power supplies in the amplifier drawer. In a standard single pallet
amplifier drawer there is only the (A8) power supply. The power supplies will operate
when AC is connected to the drawer, the CB1 circuit breaker for the (A8) power supply
and the CB2 circuit breaker for the (A9) power supply, are turned On and a Low is
provided on the Inhibit Line that connects to J1-6 on the power supplies from the control
board. The CB1 circuit breaker supplies the AC to the (A8) power supply which provides
the +48VDC to the (A1) and (A2) 878 amplifier pallets. The CB2 circuit breaker supplies
the AC to the (A9) power supply which provides the +48VDC to the (A3) and (A4) 878A
amplifier pallets.
Descriptions of External Boards Used in Transmitters w/Multiple External
Amplifier
(A5) System Metering Board (1312666)
Note: The external System Metering Board is only used in Transmitters with multiple
external Amplifier Drawers.
The function of the System Metering Board is to detect forward and reflected output power
samples and generate output voltages that are proportional to the power levels of the
sampled signals for use by the control monitoring assembly in the exciter/driver drawer.
There are two identical signal paths on the board: one for forward power and one for
reflected power. A sample of the forward output power, from the external (A11) output
coupler, enters the board at the SMA jack J3. The signal is filtered and connected to
resistors R5, R3 and R6 that form an input impedance-matching network to Pin 3 on U1.
The forward power signal is detected by the RF detector IC U1. The detected output at
pin 7 is split with one half connected to the forward average calibration pot R7, digital,
which adjusts the level of the signal connected to Pin 11 on U2.