Specifications

M.10.2 Function
Components mounted on the Switch Board/Meter Panel include
the transmitter’s on/off and raise/lower control pushbutton
switches and status indicators, forward/reflected power meter-
ing and calibration, 230VDC power supply voltage metering
and calibration control, 230VDC power supply current meter-
ing, and protective diodes and bypass capacitors for the meters.
M.10.3
Location
The Switch Board/Meter Panel is located on the back side of the
center cabinet’s front door. (SEE VIEW 13)
M.10.4
Detailed Circuit Description
Refer to the Switch Board/Meter Panel Schematic Diagram
(839- 6208-098), for the following discussion.
M.10.4.1 Pushbutton Switches S1-S6
When each pushbutton switch is depressed, it provides a +15
Volt input to the transmitter on/off control circuits on the Con-
troller Board.
M.10.4.2 Indicator Lamps DS1-DS5
The indicator lamps are physically located behind the pushbut-
ton switch caps, so that the pushbutton switch illuminates when
the indicator lamp is on. One side of each indicator lamp is
connected to the +15 Volt bus on the circuit board, and the other
side of each lamp goes to a transistor collector on the Controller
Board.
M.10.4.3 Meter Protection
Each meter is protected with two 1-Ampere diodes connected
across the meter terminals. Excessive voltage across the meter
movement will cause the diodes to conduct, shunting current
around the meter. An RF bypass capacitor is also placed across
the meter terminals. All protective components are located on
the switch board/meter panel printed circuit board.
M.10.4.4 Multimeter M1
A 2-pole 11 position switch (with 8 positions used) connects the
meter to the desired metering circuit. For voltage scales, meter
multiplier resistors are located on other transmitter circuit
boards. For current scales, the multimeter acts as a voltmeter,
measuring the voltage drop across a resistor in the desired
current path. In the PA +VDC position, potientometer R4 and
series resistor R3 are used for calibration purposes.
M.10.4.5 Supply Current Meter M2
The meter M2 is connected directly across shunt SH1. The
current shunt is connected from the negative side of the 230 Volt
power supply to ground. The voltagedeveloped across the meter
shunt is proportional to the power supply current. This voltage
is also routed to the Controller Board for overcurrent fault
sensing.
M.10.4.6 Power Meter M3
The power meter circuit includes a switch to select either the
Forward Directional Coupler output or the Reflected Direc-
tional Coupler output, and potentiometers to calibrate the meter
indications. The directional couplers are located on the Output
Monitor Board.
M.10.5
Troubleshooting
M.10.5.1 Changing Indicator Lamps
Tochange indicator lamps, carefully removethe plastic cap from
the pushbutton switch to gain access to the indicator lamp. The
plastic cap can be removed by carefully pulling it straight out
from the front of the panel.
M.10.5.2 Metering Circuit Fault
Failure of the operational amplifier driving the meter could
cause either no indication or a full scale indication. If it is
suspected that multiplier resistor values have changed value,
they can be checked in-circuit, if the multimeter is switched to
some other position to eliminate parallel resistance paths.
M-26 888-2339-002
WARNING: Disconnect primary power prior to servicing.