connection from a non-synchronous phonograph to the voltage amplifier. The second jack from the left is for use in measuring the grid "bias" voltage of the voltage amplifier. The two jacks on the extreme right are for measuring the exciter lamp current of both exciter lamps, and three jacks at the center are for measuring the plate currents of the voltage amplifier tubes.

180. Description of the PA-5 Power Amplifier Panels.- The two power amplifier panels are identical. The power amplifier units, using four UV-845 tubes each, are mounted to the rear of these panels. At the top of each panel are two plate current meters. They are recessed and protected with a pane of glass, because they are in a high voltage circuit. Holes in each panel, covered with mesh screens, permit an inspection of the UV-845 tubes from the front of the rack. The lever switch mounted in the lower left-hand corner of each panel is used to control the plate and filament circuits of the tubes. To the right of this switch are two small knobs, used for grid bias control of the UV-845 tubes. On the right-hand side of the panel is a monitoring jack for "plugging in" the monitor speaker. Below the monitoring jack is a speaker switch, which is connected between the output of the power amplifier and the loudspeakers and is used for turning "on" and "off" the output of the power amplifier.

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