Custom Audio Electronics MT558, User Manual

Page: 13 / 32

4 PRINT HEAD
MT558 has a thick fi lm thermal printhead and is allowed to have 5.0 A maximum power absorbed, the print density
variation may become larger if the number of dots energized at same time becomes greater than 64.
Scanning Line Time (SLT) is the time to print one complete line using all strobes available. The relation between the
printhead supply voltage and “On Time” (Ton) is as follows:
Po = Io
2
x Rav =
VH
2
x Rav
Ton =
Eo
(Rcom x N + Rav + Ric + Rlead)
2
Po
or
Po =
Eo
VH =
√
Po
x (Rcom x N + Rav + Rlead)
Ton Rav
SYMBOL PARAMETER VALUE UNIT
Rav Average resistance (Heater resi Lead resistance) 120 Ω
N No. of burning dots at same time (0÷192) dots
Rcom Common Resistance 0.05 Ω
Ric Driver saturated resistance 15 Ω
Rlead Lead Resistance 10 Ω
4.1 Operation precautions
When continuous printing is performed the supply energy should be reduced so that the substrate temperature 1.
show in Maximum Condition Table.
Power On and Off sequence must be in the following order to prevent the dot element damage:
2.
Turn On= Apply the logic supply voltage (Vdd) first and then the printhead supply voltage (VH).
Turn Off= Switch off the printhead supply voltage (VH)
fi rst and then turn the logic voltage (Vdd) off.
The printhead shall be disabled in STB during Power ON/OFF, or Power (VH)-Logic(Vdd) sequence described 3.
in note 2 shall be kept.
Heat elements and IC’s shall be anti-electrostatic in order to prevent the electrostatic destruction. Do not touch
4.
the connector pins with naked hands.
The printhead substrate surface is coated with glass and mechanical stress or shock (including dust scratch dam-
5.
age) should be avoided to prevent damage.
When the printhead operation is
fi nished, printsupply voltage (including the charged voltage with capacitor) should 6.
be reduced to the ground level and remained until next printhead operation occur.
Condensation should be avoided. If condensation occurred, do not switch on the printhead power until condensa-
7.
tion disappear.
Print quality would be degraded if paper or ink residue were sticked on the heat element area. For such a case,
8.
please use applicator with alcohol to clean up. Do not use the sandpaper destroying the heat elements.
If printing sound, for example sticking sound, occured, please review and adjust the paper feed mechanism and
9.
the electrical pulse to avoid these kind of mechanical resonance.
Please pay attention that the paper used does not include bad factor to affect printhead life.
10.
The print density variation may become larger if the number of dots energized at same time becomes greater 11.
than 64
value
.
In order to avoid surge, a 47 μ F capacitor is required between VH and GND at controller board side. 0.1 μ F ce- 12.
ramic capacitor should be placed between VDD and GND.
4. PRINT HEAD
User Manual
MT558 13