Back to the beginning of the Museum Web Site



235. No Sound When Using Sound Film. -No sound when using sound film may be due to a burned out exciter lamp, sound gate light aperture completely clogged, or a defective photo-cell. To determine whether the aperture is clogged or not, place a card between the sound gate and the photo-cell housing. A round circle of light should be obtained at this point. If light is obtained on the card and no sound is obtained, the indication is that the photo-cell is defective and should be replaced.

236. Low Volume When Using Sound Film. -Low volume when using sound-on-film may be due to any of the following:-incorrect exciter lamp current, dirty or old exciter lamp, exciter lamp out of focus, sound gate aperture partly clogged, or a defective photo-cell.

237. Unequal Volume From Projectors When Using Sound Film. -If unequal volume is obtained from the two projectors when using sound film, the projector giving the lowest volume should be checked for trouble. See section 236. If no cause is found for low volume the output of the projectors should be balanced by adjusting the exciter lamp currents. To do this, adjust the exciter lamp current of the projector giving the lowest volume to its usual value and adjust the exciter lamp current of the other projector to give an equal volume; then, if necessary, increase the setting of the volume control.

238. Poor Quality From Sound Film. -Poor quality of sound from sound film may be due to any of the following causes:-poor sound film, dirty sound gate, dirty film, dirty constant speed sprocket, or a defective photo-cell.

Poor quality of sound is often blamed on the equipment when the fault is in the film itself. On the other hand, dirt on the film or on the sound gate will ruin the quality of sound from a good recording.

A defective photo-cell can spoil the quality of the reproduced sound.

A photo-cell can be spoiled by misuse. It is important that the photo-cell should not be exposed to strong light at any time, whether the polarizing voltage is applied or not. They should be handled gently and not jarred. When no film is in the projector, the circle of light from the exciter lamp can be seen on the photo-cell. This circle should be located at the exact center of the plate in case of the UX868 Photo-cell or in the center of the window in case of the UX-867 Photocell. Dirty prongs on the photocell may also cause trouble. These can be cleaned readily with fine sandpaper.

After carefully checking all other possible causes of poor sound it may be assumed that the optical system is out of focus; in which case the RCA Photophone service engineer should be notified.

239. "Wows" When Using Sound Film. -If "wows" are noticeable when running sound-on-film, it may be due to dirty sprockets or due to the constant speed sprocket being excessively worn (teeth undercut). Improper adjustment of the viscous damping device will also cause "wows" and should be checked carefully. See section 92.


Chapter Fourteen Pages
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
[13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24]

[1] [2] [3] [4] [5] [6] [7] [8] [9]
[10] [11] [12] [13] [14] [15]

©1930 RCA Photophone, Inc
HTML Transcription & Graphic Reproductions ©2000 The American WideScreen Museum
All Rights Reserved