209. General Description of the PG-7 Equipment. -The PG-7 equipment is Similar to the PG-6 equipment except in the number of power amplifiers used, only two of these units being used in the PG-7 equipment, this equipment being designed for medium sized theatres. The voltage amplifier units and power amplifier units are mounted on the same rack, which is designated as the Type PA-17B.

210. General Description of the PA-17B Amplifier Rack Equipment. -Figure 123 shows the arrangement of parts on the PA-17B amplifier rack. The second panel from the top is the compensator panel. The third panel is the voltage amplifier metering panel which is identical to that used in the PG-6 and described in section 202. Below the metering panel and arranged in the order named are, No. 1 voltage amplifier control panel, the voltage amplifier switching panel, and No. 2 voltage amplifier control panel. These panels are identical to similar panels described in section 202. The voltage and power amplifiers used are two Type PA-12A and two Type PK-1 units, respectively.

Only one power amplifier control panel is used on the PA-17B amplifier. This panel is the third from the bottom of the rack and is similar in all respects to the power amplifier control panel described in section 204. The "AC LINE" switch mounted on the panel just above the power amplifier control panel is used to turn the AC power "on" and "off" of both power amplifier units.

211. Operation and Troubles on PG-7 Equipment. -The operation of the PG-7 equipment is identical to that of the PG-6 equipment and the comments on troubles of PG-6 equipments apply equally well to the PG-7.

212. Description of the PG-8 Equipments.- The PG-8 equipment is a small theatre equipment, and is similar in every respect to the Type PG-7 with the exception that the Type PA-18B amplifier rack is used. This rack is similar to the PA17B amplifier except that only one voltage amplifier unit and one power amplifier unit are used.

213. Description of the PA-18B Amplifier Rack Equipment. -Figure 124 is an illustration of the PA-18B amplifier rack showing the location of parts. It will be noticed that the panel equipment is the same as that used on the PA-17B except that there is less of it. As in the other equipments described, the compensator panel is located near the top of the rack. The metering panel is the same as that used on the PG-6 and PG-7 equipments. This panel has four metering jacks which were described in section 202, but only three of the jacks are used in the PG-8 equipment. The third jack from the left labelled "NO. 2 PLATE V" is not used, as only one voltage amplifier unit is used with this equipment.

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