The whole mechanism runs in oil, the proper level of which is about one-eighth inch below the
top of the oil cup. The turntables that do not have oil cups may have the oil level checked by
removing the turntable. The oil level should be such that one-half of the worm gear is
immersed in oil. The oil must never be allowed to drop below this position. Quaker State
Medium oil is recommended for lubricating this turntable.
The turntable is driven through a flexible steel shaft which should receive oil regularly twice a
day through the two oil holes-one at each end of the shaft.
74. Operation of Synchronous Disc Equipment - The operation of sound-on-disc in
synchronism with the picture requires that disc and film both start at definite reference points.
One frame of the film is always marked to indicate the starting point. Thread the projector,
placing the marked frame in the light aperture.
After the film has been threaded as indicated, place the record on the turntable. Use both
hands when placing or removing the record, as the hole in the record fits the turntable
spindle snugly, and the record is liable to bind if it is not level when placed over the spindle.
This binding may cause the record to become broken in an attempt to free it. After the record
is placed on the turntable, lift the pickup with the right hand, and hold it a little above the
record near the inside record groove. With the left hand rotate the record (do not move the
turntable), until the pick-up is just over the starting point of the record. This point is indicated
by a radial line, or groove, which terminates at the starting point of the spiral groove, as shown
in Figure 55. Set the pick-up needle into the groove at this point, and test its setting by applying
a slight pressure sidewise in each direction to make sure the needle is in the groove. When
this is done, the projector is ready to start in so far as the proper synchronizing of the disc and
film is concerned. Turn the projector until the turntable has rotated one-half turn to see that
the needle tracks properly.