IBM 1627 Manual page 21

5.
Rotate the adjustment knob over the full
range of its travel from -30 to +30 while
carefully observing the two idler pulleys
designated "B" and "D". There should be
no rotation of either of these pulleys. If
pulleys rotate, set the adjustment knob at
"zero" loosen nut "A" locking the pinion,
rotate the pinion slightly, and lock the
pinion by tightening the nut. Rotate the
adjustment knob again through its entire
range and observe the two idler pulleys.
If the rotation of the two pulleys has de-
creased, repeat the procedure until there
is no movement of either pulley. If the
movement of the pulleys has increased,
rotate the pinion in the opposite direction
from which it was first moved. When there
is no movement of the idler pulleys as the
adjustment knob is turned, it is then pos-
sible to set the carriage on a reference
mark at the right-hand edge of the chart
paper and make a scale factor adjustment
without disturbing the initial reference set-
ting.
With a piece of chart paper in the plotter,
and with the adjustment knob set at "zero"
draw a short vertical line near the right-
hand border of the paper. Apply 2900 input
pulses to drive the carriage toward the left
and draw another short vertical line. Re-
move the paper and measure between the
two vertical lines. The lines should be
exactly 29.000 inches apart. If the carriage
failed to move 29.000 inches, run the car-
riage to the right-hand border and loosen
the nut (designated "E") clamping the adjust
arm to the adjust cable. If the carriage
travel was in excess of 29 inches, move the
adjust arm slightly toward the rear of the
plotter and tighten the clamping nut. If
the carriage travel was short, move the
adjust arm forward. Check the carriage
travel again and repeat the procedure
above, if necessary. Fine adjustments may
be made by rotating the adjustment knob
one or two divisions and resetting the index
plate to match.
After completing preliminary adjustments, turn
plotter power ON. (Power ON will prevent the car-
riage drive pulley from turning.) Proceed to re-
calibrate the carriage scale factor adjustment as
follows:
4.
2.10
WARNING: In working upon carriage scale
factor adjustment mechanisms, use extreme
care to avoid personal contact with exposed
terminals, as well as to idler or drive pulleys
which may have applied voltages with respect
to ground.