208. Troubles on the PA-20A Power Amplifier Rack Equipment. -If one amplifier unit of the power amplifier rack becomes noisy or "dead", it will not be apparent in the operating booth unless the monitoring speaker. happens to be plugged into the defective unit. Therefore, in case of complaint, check all units by plugging the monitoring speaker successively into each of the units. When the defective unit is located, turn it "off" by means of its individual power switch and check the tubes by replacing them with tubes known to be in good condition, Be sure, also, to readjust -the line voltage to its companion amplifier to 100 volts.

Each power amplifier unit has a separate set of two fuses in the AC power line. These are usually located near the AC line plug close to the amplifier unit. These fuses should be checked if the tubes of an amplifier unit fail to light. Use Edison plug fuses no larger than 6 amperes for replacement.

Refer also to Chapter XIV.

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