200. General Description of the PG-6 Equipment. -The PG-6 equipment is the largest of the partially SPU operated equipments and is used in large theatres. It uses PS-1 sound heads and PT-2 turntables. Two amplifier racks are used; one (Type PA-19A) contains two Type PA-12A voltage amplifier units, and the other (Type PA-20A) contains four Type PK-1 power amplifier units. See sections 138 and 140. Only one voltage amplifier unit is used at a time and the power amplifier units may be used individually in case of emergency. The volume control is mounted on the voltage amplifier rack instead of on the input control panel. This input control panel (the Type PA-16B) is described in section 110.

201. Description of the PA-19A Voltage Amplifier Rack. -Figure 121 shows the arrangement of parts on the PA-19A voltage amplifier rack. The top panel is the compensator panel. The second panel from the top is a metering panel. The third and fifth panels are alike and are voltage amplifier control panels, one for each of the two separate voltage amplifier units. The fourth panel from the top is a switching panel used for switching the input and filament supply from one voltage amplifier to the other. The two voltage amplifier units are mounted in back of the five upper panels. The battery boxes for the amplifiers are mounted in back of the two bottom panels.

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