IBM 6400-I15 Maintenance Manual - Page 179

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. IMPORTANT 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 179