Thermal Head Drive; Thermal Head Outline; Power Lines - Ricoh C226 Service Manual

OPTICS/IMAGE PROCESSING

2.3 THERMAL HEAD DRIVE

2.3.1 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): White/Black pixel data
CK (CK1—CK4): To latch the shift register
data
ENL: Record control
Va: Applied voltage (16V)
VDD: Power source (5V)

2.3.2 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: 24 x 128-bit shift registers,
24 x 128-bit latches, logic gates, drive transistors, and 3072 heating
elements. The thermal head is made up of 24 drive circuits arranged in two
rows of 16 elements.
C226 2-20 SM