9-16
Phaser 440 Color Printer
9
Checks and Adjustments
Adjusting for best print quality
Thermal head temperature adjustment
This adjustments sets the reference pulse duration for the strobe pulses that
drive each thermal head element during printing. The longer the pulse duration
is, the hotter the element. During printing, the engine alters the pulse duration
slightly to compensate for ambient temperature, thermal head temperature, the
color being printed, the history of nearby printed dots and dot density. Properly
adjusting the thermal head temperature is the most significant adjustment you
can make to maximize the printer's print quality.
1.
Power down the printer. Remove the upper rear panel to access the
engine control board.
2.
Refer to Table 9-4. Set DIP Switches 2-1 through 2-8 to the setting that
matches the resistance value printed on the thermal head.
This step sets a nominal value for the thermal head. You may change
the switch setting to achieve the best print quality.
3.
Print a saturation dither pattern (test pattern 8). Refer to the earlier
topic “Printing test patterns” on page 9-2.
4.
With a properly adjusted thermal head you should see 10 steps or
color shade changes. (See Figure B-2.) If you don't see 10 steps, the
thermal head temperature is set too high and must be lowered. Set the
thermal head to the next available setting; use Table 9-4 to determine
the setting.
5.
Repeat Steps 4 and 5 until you see 10 steps in the saturation dither
pattern. Magenta is the color you should judge color levels by. Do not
try to achieve 10 steps with the color yellow. The human eye is
somewhat insensitive to shade changes to the color yellow. On rare
occasions, it may be difficult to achieve 10 levels of cyan or magenta.
It may be necessary to compromise those shades to 9 levels.
Use test pattern 5 to check and make the thermal head temperature adjustment.