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Chapter 4: Using the Printer28
A799 Two-Color Thermal Receipt Printer: User Guide A799-UG00001 Rev. D 11/2012
For reference:
• A typical receipt with text (contains some blank spaces) is approximately 12% dot coverage.
• A full line of text characters (every cell on the line has a character in it) is approximately 25% dot coverage.
• Graphics are approximately 40% dot coverage.
• Barcodes are approximately 50% dot coverage.
• A solid black line is 100% dot coverage.
Printhead Setting
The printhead energy rating and printer setting must match. The setting will be precongured from the factory but may
require changing should service to the thermal mechanism be required. The “Head Setting” on the diagnostic printout must
match the letter marked on the front right of the thermal mechanism. Whenever the thermal mechanism is replaced, if the
letter on the the mechanism is different from the head setting, you must enter the conguration menu and set the printhead
to match. (See A799 Service Guide for replacing the thermal mechanism.)
Preventing overheating of the printhead
There are restrictions on the duty cycle because of the heat generated by the thermal printhead when printing solid blocks
(regardless of the length of the block in relation to the print line). The restrictions are ambient temperature, the percentage
of time (measured against one minute) of continuous solid printing, and the amount of coverage.
Keep in mind that the ambient temperature may be affected by factors such as direct exposure to sun or close proximity to
heating elements.
Caution: When the duty cycle exceeds the limits shown in the table, the receipt printhead will heat up and shut down. This
may damage the printhead.
To avoid this problem, do one or a combination of the following:
1 Reduce the amount of coverage.
2 Reduce the time of continuous solid printing.
3 Reduce the ambient temperature.
Allowable duty cycle (measured over one minute of continuous printing)
Duty cycle
Percentage of time that the specied
“Amount of solid coverage” can be printed
during a one minute period of time.
Example: at 20% solid coverage,
35° C temperature, a 50% duty
cycle is to be used, resulting in
30 seconds of printing and
30 seconds without printing.
Amount of solid coverage Ambient temperature
25°C 35° C 50° C
20% 100% 50% 20%
40% 50% 25% 10%
100% 20% 10% 4%