Specifications

Section P
Transmitter Interface
P.1 Introduction
This section describes the Transmitter Interface board. Topics
include function, location, detailed circuit description, trou-
bleshooting, and removal/replacement.
NOTE - Parts List for this board is covered in Section VII.
P.2 Function
The primary function of the Transmitter Interface board is to act
as a tie point for inputs/outputs to and from the Controller board,
to the rest of the transmitter. In this way, the Transmitter Interface
greatly increases reliability by decreasing the number of cables
and connections to and from the circuitry mounted on the hinged
front door, most of which go to the Controller.
Other functions include Cable Interlock summing, Control Mul-
timeter monitoring, Power Supply interconnections, Battery
Backup connections, and Interlocks.
P.3 Location
The Transmitter Interface board is mounted in the center PA
compartment on the left hand wall (SEE VIEW 12).
P.4 Detailed Circuit Description
Refer to the Transmitter Interface Schematic 839-7930-512 for
the following discussion.
P.4.1
Cable Interlock
All Cable Interlock inputs from the 5 Modulation Encoders and
the Driver Encoder are applied to inputs of AND gate U3.
Provided all of the inputs are high, the output of U3-8 will also
be high and this will allow normal transmitter operation. If a
Cable Interlock - L is generated on any of the 5 Modulation
Encoder boards or the Driver Encoder board, the output of U3-8,
will go low and the Controller will shut the transmitter OFF.
P.4.2
Control Multimeter
Switch S1, along with U1 and U2, allows metering of 3 positiveand
3 negative voltages on the Control Multimeter using only 3 of the
meter positions.
With S1 relaxed, monitoring of the +22, +8, and B+ voltages is
accomplished by moving the Control Multimeter switch to the
respective positions.
With S1 depressed, monitoring of the -22, -8, and B- voltages is
accomplished using the same three respective positions on the
Control Multimeter.
P.4.3
Power Supply Interconnect
All power supply voltages from the Power Distribution board pass
through the Transmitter Interface and on to the Controller where
they are then distributed to the rest of the boards mounted on the
door. Test points, TP1 thru TP7, are provided on the Transmitter
Interface for the +22, -22, +8, -8, B+ and B- voltages.
The Controller supplies +5 VDC at J1-23 to several circuits on
the Transmitter Interface. It can be measured at TP8. This same
+5 VDC supply is then sent, via J10-35, to the External Interface
board where it becomes +5VB.
The External Interface supplies +15 VDC and -15 VDC for the
Control Multimeter on the Transmitter Interface at J10-37 and
39. These voltages can be measured on TP12 and TP13.
P.4.3.1 Battery Back-up
Battery holders for 4 AA size batteries are mounted on the
Transmitter Interface. If you desire memory back-up for longer
than 10 minutes when primary power is removed, AA size
primary cells (batteries) should be installed in the holders. Di-
odes prevent reverse current flow through the batteries.
NOTE
Do not use rechargeable batteries, such as NiCad batteries. This
circuit is not designed to recharge batteries.
Ordinary carbon batteries can be used, but alkaline batteries are
recommended, as they are less likely to leak and their longer
“shelf life” will be an advantage in this low-current application.
Note
Do not install back-up batteries unless C46 and C47 are charged
(+5B voltage at TP16 is greater than 4.5 Volts). Current drain
from the batteries during charging of C46 and C47 will shorten
battery life.
P.4.3.1.1 Replacing Batteries
Because of the very low current drain, the life of back-up batter-
ies should approach the battery shelf life. It is recommended that
batteries be replaced at least once every 6 months. This will
ensure that they will operate properly should they be required.
P.4.3.1.2 External Battery Input
Any +6VDC voltage source may be connected to TB1-1 (+) and
TB1-2 (-) to be used as a battery backup.
Both the External Battery Input and the Internal Batteries are
connected to the Controller at J16-12.
P.4.3.1.3 Power Supply Monitor
U5 normally connects the +5VDC supply from the Controller at
J1-23 to the +5VDC output that is connected to the Frequency
Control Interface. If AC power is lost, at the point where the
Controller will switch to the Battery supply at J16-12, U5 will
also connect the +5VC supply to J16-12, via 3 dropping diodes.
The +5VC supply is used to maintain memory for the frequency
control circuits.
888-2339-002 P-1
WARNING: Disconnect primary power prior to servicing.