Ricoh PRIPORT VT 2000 Series Service Manual page 73

28 February '91
2.10 THERMAL HEAD DRIVE:
2.10.1 Function/Specification
The VT2130/VT2150 use the A4 size (216 mm width) thermal head and the
VT2100/VT2300/VT2500 use the B4 size (256 mm width) thermal head.
Thermal head
•
•
•
•
2.10.2 Thermal Head Outline
A thin-film type thermal element is used in the thermal head. The drive
circuit has a 1-line buffer for serial input. Each thermal element has direct
drive due to switching elements.
S1 (S11----S18):
CK (CK1----CK4):
ENL: Record control
Va: Applied voltage (16V)
VDD: Power source (5V)
2.10.3 Power Lines
VCC/VHD/GND .... Applied voltage
VHD:
As the resistance of the thermal elements varies depending on the thermal head, it
is necessary to adjust the applied voltage according to the average resistance of
the thermal head.
The thermal rating of each head is documented on the thermal head cover.
Therefore, after installing a new thermal head, always recalibrate the power supply
unit according to the VHD ratings on the thermal head cover. Adjust VHD using
VR201 on the power supply unit.
The drive circuit (LSIC) consists of the following: 32 x 128-bit shift
registers, 32 x 128-bit latches, logic gates, drive transistors, and 4096
heating elements. The thermal head is made up of 32 drive circuits
arranged in two rows of 16 elements.
NOTE: The thermal element used on the VT2130/VT2150 is narrower
than the B4 thermal head. Therefore, the shift registers, latches,
logic gates, and drive transistors located on both ends have been
deleted from the thermal head.
Memory length
Number of thermal heating elements
Density of thermal heating elements
Applied Voltage
White/Black
pixel data
To latch the
shift register
data
Va
(16V)
1 2
VDD
VDD
VDD
2-46
256mm (B4)
216 mm (A4/LG)
4096 dots (B4)
3456 dots (A4/LG)
16 dots/mm
16V(14~18V)
126
3
128 bit LATCH
128 bit Shift Reg
127 128