line should not deviate from its correct position
by more than the width of one recording dot or
a. Line Feed Pattern.
Line feed pattern (fig.
elemental area. This is approximately one one-
as a result
of irregular longi-
hundredth inch. A bind in the drum and the
tudinal travel of the drum. If the drum does not
lead-screw system causes jitters which will be
advance uniformly at the rate of 1/96 inch per
aggravated considerably if the synthetic rubber
revolution, some of the photographically recorded
plate is too soft.
scanning lines will overlay and others will under-
lap, thereby creating a blank space between the
two lines. If the effect is great enough to cause
rective measures must be taken. The most
common cause of trouble is the drum and lead-
screw system. First check the arm of the drum-
feed engaging mechanism to be sure it is riding on
the guide rail. Install new half nuts as a correc-
tive measure. Be sure that the snubber (N, fig.
firmly against the lens barrel.
does not correct the trouble, make a test recording
by substituting the drum of another machine.
Be sure that the test recording is of the same type
and is made by the same method as the one on
which the line feed pattern proved troublesome.
c. Irregular Skew. If the receivced copy shows
A final test should be made by using both the
drum and the lead screw of another machine.
If the line feed trouble remains, the trouble is
slipping. This slippage often can be traced to a
probably in the motor or the optical system.
bind in the drum system. To determine whether
b. Jag or Jitters. These are the terms used to
the defect is in the transmitter or receiver,
describe irregular or saw-tooth recording of lines
examine the recorded copy with a magnifying
glass. If the individually recorded elemental
generally in the motor or the clutch. It can,
areas are in approximate straight alinement, the
however, originate in the drum or the lead screw.
To determine whether it is in the drum or the
the contour of the skew, the trouble is in the
lead screw, first replace the motor with one from
recorded system. When receiving on direct re-
another machine which is operating satisfactorily,
cording paper, observe the direction of the skew
and make a test run. Use a transmission test
before removing the paper from the drum. If
copy having straight lines running parallel to the
the right-hand side of the copy is skewed toward
axis of the drum. The recording of the straight
the rear of the machine, the clutch is slipping in the