181. Description of the PA-5 Control Panel. -The control panel of the PA-5 amplifier rack is
usually mounted between the two power amplifier panels. The knob at the center of this panel
is the field rheostat knob for controlling the field current, and therefore the generated voltage,
of the 250 volt generator.
Only one field rheostat is used on this equipment. The field current of the 15 volt and 1000 volt
generators is supplied by the 250 volt generator, but instead of using a field rheostat for each
machine fixed resistors are used with the 15 volt and 1000 volt generators. Therefore it is only
necessary to adjust the voltage of one generator, as the voltages of the other two generators
will then be automatically adjusted to their correct values. It is advisable to adjust the rheostat
to give the proper voltage from the 15 volt generator because this voltage should be adjusted
to keep the storage battery properly charged.
The two jacks at the left-hand side of the panel are for use in measuring the plate voltage of
the voltage and power amplifiers. The two jacks on the right-hand side of the panel are for
measuring the voltages of the 250 volt and the 15 volt generators. The switch in the lower
right-hand corner of the panel is for starting and stopping the motor-generator set. To the left
of this switch is a pilot lamp which is lighted when the motor-generator set is running.
182. The PA-5 Loudspeaker Switching Panel. -The loudspeaker switching panel is usually
mounted on the side of the rack. It has six snap-switches. Three of these switches are
connected to the output of one power amplifier and the other three are connected to the
output of the other power amplifier. They are used to switch off individual speakers or groups
of speakers in case of trouble, or in case it is not desirable to operate all of the speakers.
These switches are not otherwise used in the operation of the equipment. This panel is not
illustrated in the figures.
183. Operation of the PG-2 Equipment. - Before starting the motor-generator set see that the
commutators are clean and smooth and that the bearings are well oiled. See section 36.
The voltages of various circuits should be checked whenever the equipment is started up, but
before checking the voltages see that all the amplifier rack power switches are turned "on."
That is, see that the two exciter lamp switches on the
voltage amplifier panel are in their "ON" positions and that the lever switches or the power
amplifier control panels are in their "up" positions, except when only one power amplifier is to
be used, in which case one power amplifier lever switch should be left in its "down" position.