Hammer Phasing - IBM 6400 series Maintenance Manual

Hammer Phasing Adjustment
You must check and adjust hammer phasing if the CMX controller board is
replaced, the shuttle frame assembly is removed, or if the MPU is replaced.
The hammer phase value is a timing parameter that permits you to adjust the
horizontal alignment of dots in character printing. The phase value numerical
units are relative; they do not represent a physical measurement or value.
Thus there is no "correct" value or range. But, if the phasing value is far
enough from the theoretical ideal value on a particular printer, errors can
occur. If, for example, you are adjusting phasing and an error such as 124
PAPER FIFO UNDERFLOW occurs, the phase value may be too high. Try a
lower value.
The factory prints the initial phase value on the aluminum casting of the
shuttle assembly, next to the motor housing. Adjust the phasing to this value
and recheck the horizontal alignment. When alignment is acceptable, write
the new phasing value on the shuttle.
Phasing should be adjusted with the printer printing at full paper width.
The printer must be printing the Phase pattern of "H's" when the
Phasing Value is changed, or the New Phasing Value will not be written
into NVRAM. If the value is changed when not printing, the printer will
return to its default phasing value when powered off then back on.
1. Power on the printer.
2. Install the ribbon.
3. Load full width (136 column) paper and set the top of form.
4. Press Stop to put the printer into NOT READY mode.
5. Press Scroll" + Scroll# to unlock the Enter key.
6. Press Scroll" + Scroll# + Return + Enter to enter the CE Tests menu.
(Press all four keys at the same time.)
7. The display will show "SERVICE / PRINTER MECHANISM TESTS", the
first menu item. Press Enter to enter the mechanism tests menu.
8. Press Scroll" or Scroll# until
"PRINTER MECHANISM TESTS / HAMMER PHASING" is on the
display.
Adjustment Procedures
IMPORTANT
179