protect the MOSFETs against excessive source-to-gate voltage.
Diode CR15 protects the regulator circuit against negative tran-
sient voltages.
Resistor R42 provides negative feedback around the regulator
section.
E.4.8
Metering Circuits
RF Driver voltages and currents are metered on the RF MUL-
TIMETER.
E.4.8.1
Reference Voltage (CVDC)
The RF level reference voltage outputs from U2A or U2B are
metered in the “CVDC” position. R4 is the meter
multiplier resistor. The CVDC voltage is also sent to
the Driver Encoder/Temp Sense Board through R5.
E.4.8.2
115 VDC PA Supply Voltage (VDC)
The +115 VDC supply voltage is metered in the VDC
position. The +115 VDC is sampled at the supply side of R3 and
enters the Driver Supply Regulator at J2. Resistors R46, R47, R48,
and R49 form the meter multiplier circuit used in this position.
E.4.8.3
Driver Current Metering (“DRIVER IDC”)
The “DRIVER IDC” position of the RF Multimeter reads total
Driver current. All Driver current passes through the three 0.1
Ohm resistors R3A, R3B, and R3C, and the voltage drop across
the resistor is measured. Resistors R44 and R45 are voltmeter
multiplier resistors.
E.4.8.4
Driver Amplifier D8 Voltages (DRIVER 8A +VDC)
and (DRIVER 8B +VDC)
The Driver Supply Regulator output voltages feeding D8A and
D8B are metered in these two positions. R54, R55, R56, and R57
are the “A” circuit meter multiplier resistors while R50, R51,
R52, and R53 form the “B” circuit.
E.5
Troubleshooting The Driver Supply
Regulator
Troubleshooting the Driver Supply Regulator can be done by
first checking for proper operation of the regulator, then, if the
fault is determined to be in the regulator assembly, removing the
assembly and making out-of-circuit measurements to locate the
fault.
Because the operation of the Driver Supply Regulator is depend-
ent on the overall drive from the Driver Stage, the voltage
readings of D8A and D8B can change under various conditions.
If the AC line voltage changes, the DC voltage to the Driver
Modules will change and the Driver Supply Regulator will vary
the voltage to D8A and D8B to compensate.
Figure E-1. Driver Supply Regulator
Simplified Schematic Diagram (817 2099 028)
Section E - Driver Supply Regulator (A22)
888-2297-002
E-3
WARNING: Disconnect primary power prior to servicing.
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