106. Oiling Points on the Motor Side of the Type PS-14 Sound Head. (Used with the Power's Projector with DC Motor Drive).-No illustration is given. The method of oiling is essentially the same as that given for the sound head with Power's Projector with AC motor drive-the DC sound head being equipped with direct gear drive the same as the AC sound head. The DC motor bearings are packed in grease, and will be taken care of by the RCA Photophone representative.

107. Re-Winding Film and Painting Splices. -Particular care should be taken when handling sound film to keep it clean and prevent it from being scratched. When re-winding film see that the reels have no rough edges which might scratch the film. Line up the reels so as to prevent the film from rubbing against the sides of the reels. Scratched or dirty film will give poor sound reproduction.

When a break occurs in a sound film it should be patched in the usual manner, but the sound track requires special treatment. The sound track should be painted as shown in Figures 72 and 73. Paint a half moon over the sound track if the recording is variable area, and a blunt apex if the recording is variable density. Use Zapon concentrated Black Lacquer No. 2002-2.

108. A Few Items to Remember when Using Sound-on-Film.-

See that the sound gate is closed while running the projector. An open sound gate will cause poor intelligibility of sound reproduction and may result in damage to the film.

Keep the film clean. Dirty sound film means a poor picture and poor sound.

Paint your film splices. Poor splices in sound film produce "plunks" in the loud speaker.

Keep the sound film clean. Emulsion and dirt on the sound gate will cause a "flutter" in the sound at the higher frequencies.

Keep the optical system clean. A dirty or oily lens in the optical system will produce "fuzzy" or "mushy" sound reproduction.

Do not permit dust and dirt to collect on the surfaces of the photo-cell or the lens ahead of it. Dirt on these surfaces will cause loss of volume.

See that the photo-cell is inserted all the way down in its socket. An improperly inserted photo-cell will cause poor contact and will result in noisy reproduction. It may also cause a reduction in volume.

Keep the door of the photo-cell housing closed to exclude outside light. If outside light comes from an alternating current source, it may cause a very undesirable hum in the speaker.

Be sure that the door of the sound head is closed to exclude light. The reason for this is the same as above.

Always have an extra exciter lamp set up ready for an emergency on Types PS-14 and 16 sound heads, or have a complete set of good lamps set up and focused in the Types PS-1, 5, 6 and 8 sound heads.

Keep both exciter lamps lighted at all times during the show when running sound-on-film.

Be sure that the exciter lamps are properly adjusted vertically. Improperly adjusted exciter lamps will result in a decrease in volume and possible "fuzzy" sound reproduction.

Keep the light aperture in the sound gate clean, and be careful oil does not get into it. Oil in the light aperture may result in "fuzzy" sound from the speakers.

Copyright 1930 RCA Photophone, Inc 15