AR 20S6G18-L, Operating And Service Manual, Page: 36 / 50

Model 40S6G18-L
20 Rev E
3.2.4 A4 & A5 20-Watt Modules
IC U2-U5 are current sense amplifiers with a current limit of approximately 4 amps for each IC. Each IC
monitors the current of 4 FET’s. If overall current for each IC falls below or exceeds certain current limit, a
fault is displayed on front panel and i10V to preamp.
A 4-way splitter at the input of the 20-watt module feeds 4 RF channels. All RF circuits are assembled on
thin film substrates. The output of the RF channels are then tied to a 4-way combiner. Each module has a
gain of approximately 18 dB or greater and delivers approximately 20 watts of RF power.
3.3 POWER SUPPLY
There are two power supplies in the 40S6G18-L amplifier.
Power supply PS1 is a switching supply that automatically sets the AC input circuits to the correct
connections for the line voltage 90-132 and 180-250 VAC input ranges 50/60 Hz. The outputs of +24, +12
and -12 volts are used primarily in the A1A1 preamp module, control panel A12A1 and interface board A14.
-5V is also used as a gate bias in the driver amplifier A1A2 and 20 watt amplifiers A4 and A5.
Power supply PS2 is also a switching supply that automatically sets the AC input circuits to the correct
connections for the line voltage 90-132 and 180-250 VAC input ranges 50/60 Hz. This power supply is
responsible for the +26.3 V drain bias to the driver amplifier A1A2, and 20 watt amplifiers A4 and A5.
3.3.1 A7 Regulator Fault Board (Schematic #10044490)
The A7 regulator fault board uses one regulator to c24V to +15V to the A1A1 preamp.
The A7 regulator fault board also has two regulators to convert the -12V to -5V for the A1A1 preamp, A1A2
driver and A4/A5 20 watt modules.
3.4 CONTROL SYSTEM
3.4.1 A12A1 Control/Fault Board (Schematic # 10029678)
The A8 Control/Fault board consists of two 16-bit microcontrollers and about nine other ICs that monitor and
indicate the status of the amplifier. Power is supplied using only a single 5-volt power supply. The board
offers the following:
Feature Quantity
Open drain outputs 2
Digital outputs 12
Digital inputs (5-volt tolerant) 24
Analog outputs 2
Mixed signal inputs 4
2-channel encoder input 1
Inputs for a keypad 8
Display connectors 2
Serial communication jacks 2
3.4.2 A14 Interface Board (Schematic # 10020073)