IBM 6400 series Maintenance Manual page 128

Clean the shuttle frame assembly and hammer bank cover assembly if
you find debris. Replace the hammer bank cover assembly if you find
any damage to the ribbon mask or hammer bank cover.
5. Power up the printer. Run a shuttle test.
Replace the shuttle frame assembly if it is noisy or rattles.
Stacker chatters at upper or lower limit
1. Check for obstructions preventing elevator movement.
Remove obstructions.
2. Check for misaligned stacker rails
Adjust the stacker rails if they are not vertical and parallel.
3. Move the elevator up and down by hand. Check that the limit switches are tripped
when elevator reaches top and bottom of travel.
If necessary, gently bend contact arms to adjust limit switches. If you
cannot adjust a switch that requires adjustment, replace it.
4. Power on the printer. Operate the power stacker. (Refer to the Operator's Guide .)
While the stacker is operating, check that:
a) all motors are operating
b) the paddles are rotating
c) the elevator moves smoothly and without obstruction
d) the timing belts are undamaged and the belt pulleys are not slipping
e) the extension springs are attached and undamaged (not bent or stretched)
f) the drive rollers are not damaged
g) the constant force springs are tightly mounted and undamaged
Tighten pulley setscrews and/or replace damaged components as
necessary.
Stacker does not stack properly
—or—
Stacker elevator does not move
1. Check for obstructions preventing elevator movement.
Remove obstructions.
2. Check for misaligned stacker rails
Adjust the stacker rails if they are not vertical and parallel.
3. Power on the printer. Operate the power stacker. (Refer to the Operator's Guide.)
While the stacker is operating, check that:
128 Troubleshooting