Power Supply/RF Board
4-18 Force FX-8C Service Manual
Power Supply/RF Board Interfaces
The Power Supply/RF board interfaces to other boards and components
as noted below:
• AC input line filter
• Control board
• Footswitch board
• Heat sink components (RF damping resistor, RF MOSFET, and high
voltage power supply MOSFETs)
• Single-wire attachment points for connecting the sense transformers
• Low voltage power supply (AC input and DC output)
• Low noise fan.
A series of fuse clips connect the RF outputs and other front panel
interfaces (i.e., REM and handswitching signals). The fuse clips mate to
lugs located in the output portion of the front panel.
High Voltage Power Supply
The high voltage power supply section contains the power entry circuitry,
auto mains switching circuitry, AC/DC conversion circuitry, and a
DC/DC switching regulator.
Power Entry Circuit
The power entry circuit consists of an integral three wire power cord
receptacle, fuse drawer, EMI filter, and a separate power switch. The
power switch is mounted on the front panel. The receptacle/filter is
mounted on the rear panel of the generator. AC line fuses are changeable
from the rear of the generator.
Auto Mains Switching Circuitry
The auto mains switching circuit detects the AC line voltage level and
controls the triac (D1). This triac controls the topology of the AC/DC
converter. For 120 Vac operation, the triac is on, which connects the AC
neutral to the center of the AC/DC converter capacitor bank (C3, C10,
C11, and C22). In this configuration, the circuit acts as a doubler using the
right hand half of the bridge rectifier (CR80). For 240 Vac operation the
triac is off and CR80 is used as a full wave rectifier.
The control IC (U1) functions as follows: The series circuit (CR1, R1, R2,
and C9) provides power for U1. Pin 1 (Vss) is a shunt regulator that
provides a –9 V (nominal) output. The divider (R3 and R4) measures the
Warning
Potentially lethal AC and DC voltages are present in the AC line circuitry, high
voltage DC circuitry, and associated mounting and heat sink hardware described
in this manual. They are not isolated from the AC line. Take appropriate
precautions when testing and troubleshooting this area of the generator.
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