Specifications

4.7 Drive Multimeter
4.7.1 Introduction
This section describes the Drive Multimeter board.
The Drive Multimeter provides metering of the Predriver and
RF Driver sections of the transmitter. A probe, with four meter
positions, is also provided for ACand DC voltage measurements
on printed circuit boards in the transmitter’s non-interlocked
compartment.
4.7.2
Location
The Drive Multimeter is located on the back side of the right PA
compartment front door. (See Fig. 4-9).
4.7.3
Principles of Operation
The meter has a 100 microampere movement, and two scales,
0-3 and 0-10. The meter switch positions are labeled with the
name of the metered function and the scale used. For some
positions, a X10 or X100 multiplier is applied to the meter scale
reading.
Refer to the Drive Multimeter schematic diagram for the follow-
ing circuit discussion. Meter M1 is protected against excessive
voltages and currents by 1-Amp rectifier diodes CR4 and CR5.
Capacitor C3 provides an RF bypass around the meter move-
ment.
4.7.3.1 Metering Driver Section Parameters
For 0-3 Volt, 0-30 Volt, and 0-300 Volt DC ranges, the multime-
ter is a 10,000 Ohms per Volt meter. For currentranges, the meter
acts as a voltmeter, measuring the voltage drop across a resistor
in the DC current path. One side of the meter is grounded
through a section of switch S1 for driver section voltage meas-
urements. The meter is isolated from ground for current meas-
urements.
Figure 4-9. Driver Multimeter Switch
Location and Positions
4-16 888-2339-002 12/16/03
WARNING: Disconnect primary power prior to servicing.