If closing the power amplifier lever switches does not cause the fuse to blow,
turn the exciter lamp switches to their "On" positions, one at a time. If the fuse blows when one of these
switches is turned "on" the indication is that the shortcircuit is in the exciter lamp circuit of the
projector whose exciter lamp control switch causes the fuse to "blow." As in the case of the PG-1, the
equipment can be operated for sound-on-film from one projector and for sound-on-disc in case of a
short-circuit in the exciter lamp circuit of one projector, by leaving the exciter lamp switch associated
with the defective projector in the "Off" position.
248. Short-circuit on the "A" Supply Line of a PG-13 Equipment. -In case of a short-circuit on the "A"
supply line of a PG-13 equipment, a fuse will "blow" in the low voltage generator circuit, and the
filaments of the amplifier tubes and the exciter lamps will not light.
To isolate the short-circuit, turn the exciter lamp rheostats on the projectors to their "Off" positions and
replace the blown fuse. If the fuse "blows" before the exciter lamps are turned "on" the indication is
that the short circuit is either in the filter unit or in the amplifier unit. If the f use does not blow when the
exciter lamp rheostats are in their "Off" position, turn "on" the exciter lamps one at a time. The exciter
lamp circuit which causes the f use to "blow" should be left turned "off " so that the equipment can be
operated from disc as usual or from sound-on-film from the projector the sound circuits of which are
249. Type PK-1 Power Amplifier Tubes Fail to Light. -If the Type PK-1. power amplifier tubes fail to light,
check the fuses in the AC line. If there is a reading on the volt-meter located on the front of the power
amplifier control panel, the line fuses have not blown. In this case, check the fuses mounted in the
amplifier unit. These fuses should never be more than 6 amperes rated capacity. If the fuses continue to
blow and the installation has more than one power amplifier, turn "off" the amplifier that is causing the
fuses to blow and operate on the others.
In the PG-10 equipments there is a cartridge fuse mounted on the rear of the power amplifier control
panel of the amplifier, Type PA-21A. This fuse should never exceed 6 amperes rated capacity. In case
the power amplifier tubes fail to light, check this fuse. If it is blown, no reading will be obtained at the
In the PG-4, PG-8 and PG-10 equipments only one power amplifier is used and an attempt should be
made to correct the trouble immediately. Replace all the tubes with tubes known to be in good
condition and try the amplifier again. If the tubes do not light or the plates of any of them should
become red hot, the indication is that the unit is defective and cannot be used.
250. Noise or "Motor-Boating" When Using Either Sound Film or Discs-Noise or "motor-boating" may
be due to any of the following causes:-
(a) Dirt and acid on top of the storage battery. Switch to the other battery and clean the dirty one.
(b) Gassing storage battery. Do not use a storage battery sooner than one hour after charging, unless
in an emergency.
(c) Loose storage battery terminal connections. Clean and tighten.
(d) Loose connections to dry batteries.