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To operate the voltage amplifier, turn the battery switch "ON". The filaments of the voltage amplifier tubes and the exciter lamps on the projectors should then light. One of the voltage amplifier indicator lamps will light, indicating which voltage amplifier is connected. To change from one voltage amplifier to the other, switch all three voltage amplifier switches and make certain that they are all either in the "NO. 1" or in the "NO. 2" position. If any one switch is set in a different position from the others "no sound" will result. Switch the output changeover switch first, and then switch the other change-over switches as nearly simultaneously as possible, otherwise a severe popping noise will be produced in the loudspeakers.

192. Operation of the PA-17A Power Amplifier Control Panel. -Turn both power amplifier switches "ON" and adjust the AC line voltage to 100 volts by means of the line rheostat. The AC voltmeter indicates the line voltage. The performance of both power amplifiers should be checked by plugging the monitor speaker into each monitor jack. After checking both amplifiers the monitor speaker should be left plugged into one of the monitor jacks.

193. Troubles on PG-3 Equipments. -Trouble from "run down" dry batteries can be prevented by periodically checking their voltages as outlined in section 191.

Should one voltage amplifier give trouble during operation, switch over to the other voltage amplifier, and, when convenient, check the tubes of the defective amplifier by replacing them with tubes known to be good. If the trouble cannot be readily located notify the RCA service man.

Should trouble develop on one of the power amplifier units, it will not be apparent in the operating booth if the monitor is plugged into the good amplifier. Therefore, both amplifiers should be checked in case of complaint. If one amplifier goes "dead" the speakers connected to it will also go dead. In such a case turn "off " the defective amplifier, and, unless it is obvious that some other defect is causing the trouble, check all tubes in the amplifier by replacing them with tubes known to be good. In case the output of one amplifier is noisy and the other is O.K. turn "off " the noisy amplifier and check the tubes.

If it becomes necessary to turn "off" one of the power amplifiers be sure to readjust the line voltage to 100 volts as before.

For a more complete description of the troubles which may be experienced with the PG-3 equipments, see Chapter XIV.


Chapter Thirteen Pages
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