Harris ZX10, Technical Manual

Page: 92 / 198

4-12 888-2595-001 12/20/11
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WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
ZX Series
A socket interlock is provide by a jumper connection between pins J1-A and J1-V.
Circuits on the PA backplane will not supply 50V power to module until the J1-A to J1-
V connection is satisfied.
4.12 Transmitter Controller PCB
Consult drawing 801-0203-541
The transmitter controller board serves as both the main interface to the user and the
principal control point to set the operational state and power level of the whole
amplifier chassis. It provides the following major functions:
•
Sets the on/off state of the amplifier
•
Controls the RF power level via an automatic power control circuit (APC)
•
Determines the operating mode (FM/FMHD/HD) and sets the PA and IPA
bias voltages accordingly
•
Displays meter readings for various parameters
•
Signals the existence of fault conditions
•
Provides a means to adjust the drain voltage
•
Senses the ambient temp at the air inlet
4.12.1 On/Off Control
The transmitter on/off state is held in memory by non-volatile flip flop U13 (page 4).
U13 is a type D flip flop. It will change state whenever its clock pin (pin 5) experiences
a low-to-high transition. The new output state at pin 3 depends on the state of input D1
at pin 6 when the clock transition occurs. A high logic output corresponds to a
transmitter on condition, while a low logic output corresponds to a transmitter off
condition. Optoisolators U30A and U30B apply +5V to the D1 input and/or clock input
whenever their LED cathodes (pin 2) are grounded via either the local on-off
pushbuttons or via a connection to the remote control ON_CMD_BUS and
OFF_CMD_BUS if remote control has been enabled.
NOTE:
The on command provided via the front panel pushbutton or remote control inter-
face must be momentary (pulsed). Ensure that any external remote control sys-
tem is programmed to send a momentary (non-latched) ON command.