The viscous damping grease cup, where used, should be filled with genuine Alemite grease, and the
grease cup given a half-turn down each time the projector is put into use, or once for every two hours
of continuous running.
Pad rollers provided with oil holes, guide rollers on the sound gates and fire trap rollers should receive
one drop of light machine oil for each day's use. Apply with a tooth-pick.
After lubrication, all excess oil should be wiped off of the projector mechanism. Particular care should
be taken to see that no excess oil is left on the pad rollers, lateral guide rollers, idler rollers, and fire trap
rollers, because these parts come in contact with the film. If oil should get on the film it would impair the
picture and sound reproduction.
In addition to the oiling noted in the foregoing paragraphs attention should be given to the gears,
racks, and pinions of the projector mechanism which are not oiled by means of oil holes. An occasional
drop of oil on these moving parts will increase the life and improve the performance of the projectors.
275. Description of Amplifier. -The amplifier for the PG-5 equipment operates on any 110 volt, 50 to 60
cycle alternating current supply, available almost everywhere. Converters are available where DC must
be used. See section 35. No batteries are required. It is housed in a metal cabinet and is connected to
the projectors, loudspeaker and source of supply by easily connected cables. The amplifier proper
consists of two stages of voltage amplification and one power stage. The output of the photo-cell
transformer is auto-transformer coupled to the grid of the UY-224 screen grid Radiotron. The output of
this tube is impedance coupled to the
grid of the UY-227 Radiotron, and the output of the UY-227 tube is impedance transformer coupled to
the grid of the UX-250 Radiotron. The output of the UX-250 is impedance-transformer coupled to the
voice coil of the loudspeaker. The volume control consists of a variable resistance connected across
the input to the amplifier.