264. AC to DC Motor-Generator for DC Projector Drive Motors. -The motor starting boxes for this set do
not contain fuses, but contain instead an overload switch which turns "off" the power to the motor in
case of trouble. If, for any reason, the motor draws excessive current, this overload switch will trip. It will
not be possible to start the motor until the overload switch has been reset by hand. The reset is operated
by pulling up a lever which protrudes from the right-hand side of the starting box, or by pulling a cord
hanging from the box. If at any time, the motor fails to start when the push buttons are operated, operate
this reset to make sure that this switch is closed. In an emergency it is not necessary to push the "Stop"
button of the machine that is operating, just push the "Start" button of the other. This stops the motor
generator that is running and starts the other.
If the machines run but no voltage reading is obtained at the DC voltmeter, check the fuses on the front
of the generator control panel. Also note if the selector switch on the front of the panel is closed for the
proper generator that is running. See section 33.
265. DC to AC Motor-generator Sets. -If the DC to AC motor-generator set fails to start when the motor
line switch is closed, look for blown fuses in the line starter box. See section 34.
In case of the ½ k-va set, if the set runs and no AC power is available at the power amplifiers and a
reading is obtained on the AC voltmeter at the M-G set, the indication is that the fuses under the mesh
cover of the set (see Figure 26) are blown. The mesh cover can be removed by removing the three nuts at
the end of the tie rods at the back of the panel.
In case of the 1½ k-va set the AC line fuses are mounted just above the AC voltmeter on the generator
control panel (see Figure 28). If one of these fuses should burn out, no reading will be obtained on the
AC voltmeter when the M-G set is running.
CAUTION.-A DC motor field rheostat is mounted on the generator control panel of the
1½ k-va M-G set. The setting of this rheostat should not be disturbed by the projectionist.
266. DC to AC Converters for SPU Equipments. -Very little trouble will be experienced with these
machines and, if there is a spare, in case of trouble change converters. If this does not remedy the
trouble, check the AC fuses in each supply line and if they are O.K. and the converter is running but no
voltage is obtained in the amplifier, check the fuses in the amplifier itself.