User's Manual

Innovator CU5-1800BTD/BRD ATSC Transmitter/ Board Descriptions
Regenerative Translator
Instruction Manual, Rev. 0 54
(A9 & A10) Power Supplies used in CU5, CU30, CU50, CU100 & CU125 and
Driver for CU250 & higher power
Voltages for the operation of the boards in the tray are generated by (A9) a +5VDC and
±12VDC power supply and (A10) a +28VDC power supply for the CU30, a +30V supply
for the CU50 and Driver for the CU250 and higher power, +39VDC for the CU100 &
CU125, and +24VDC for the CU3. The 115VAC or 230VAC input to the CU3-CU50 tray
connects through the AC power cord at J6, the power entry module located on the rear
panel of the tray.
The CU100/125 tray only operates with 230VAC. An On/Off 10A/250VAC circuit breaker
is part of the power entry module. With the circuit breaker switched On, the (L) line
input is wired to F1 a 10 Amp fuse for over current protection. The AC lines are
connected to terminal block TB1, which distributes the AC to (A9 and A10) the two DC
power supplies. There are two varistors, mounted on TB1, connected from the line input
to neutral and to ground for surge protection. The AC in the CU100/125 also connects
to the (A11) fan mounted on the rear panel of the tray. The fan will run when AC is
applied to the tray and the circuit breaker is switched On. The +5VDC and ±12VDC
outputs of the (A9) power supply connects to the terminal block (TB2) that distributes
the DC to the boards in the tray. Some of the +5VDC and ±12VDC outputs connect
directly to the 8 VSB Demodulator and 8 VSB Modulator boards while the other outputs
connect through the CU Control Board to the IF Precorrector, the Digital Upconverter,
the ALC, the Amplifier Assembly and the Output Detector Boards.
The +24/+28/+30/+39VDC outputs of the (A10) power supply connect to the (A8) CU
Control Board, which then supplies the switched +24/+28/+30/+39VDC to the (A6)
Amplifier Assembly. In CU3-CU50 trays the DC output of the (A10) power supply also
connects to the (A11) fan mounted on the rear panel, which will operate when AC is
applied to the tray, the On/Off circuit breaker is On and the (A10) power supply is
operating.
Circuit Description of External Board only used in CU250 and higher power
Transmitters with external amplifier trays
(A5) System Metering Board (1312666)
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 tray.
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. The other half of the split
is connected to the peak calibration pot R18, analog, which adjusts the level of the signal
connected to Pin 8 on U2. U2 is a Bilateral Switch IC whose output, digital or analog, is
controlled by the selection of the modulation type in the exciter/driver tray. In this BTC
transmitter the average, digital, output connects to the amplifier IC U3A that is wired to
the SYS_FWD and RMT_FWD Power Metering Outputs. A reading of 2 VDC measured at