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pressure on the aperture pressure-plate will stop the jumping till the show is over.
Examine sprockets for wear, and also the claws if fitted. Make sure that the film perforations are not torn or strained.
Flicker
This may be caused by the projector running too slow, or because the shutter has become slightly displaced and is thus out of time with the mechanism.
Irregular flickering of the lamp is another fault, caused by poor contacts in the lamp circuit, or perhaps because the lamp is not properly seated.
A mercury-arc lamp may also produce a "beat" if used without proper accessories, or unless the speed of the projector is increased or decreased by about one frame per second.
Irregular Take-up
"Snatching* ' of the take-up is caused by the belt slipping, or perhaps by the belt catching in some part and being momentarily checked. See that the connecting link in the belt is not the cause of the trouble, especially if projecting with the belt crossed * Excess heat, or undue noise in the take-up head may be the first sign of wear. If the condition is bad, remove the belt and take up the film by hand-winding the spool ; this will save further damage to the perforations.
Usually, however, the cause of the trouble is skidding (instead of gripping) of the wire belt, and there is no reason why the operator should not try to cure this trouble without stopping the show. Grease can be removed by wrapping a piece of cloth around a finger and then pressing with it against the inside of the belt. Providing that the cloth is held taut, there will be little chance of it being caught in the belt, as would be the case if the cloth were loosely held or wrapped entirely around the belt.
Take-up Failure: (A) Direct Drive, (B) Belt Drive
(A) Failure of the take-up may be caused by the transmission at fault, or because the take-up arm has become disconnected. Transmission faults include a bent spindle or perhaps
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