Thermal Head Control; Specifications; Thermal Head Protection - Ricoh C231 Service Manual

IMAGE PROCESSING
6.4.8 THERMAL HEAD

Specifications

Length:
Number of thermal head elements: 3456 dots
Density of thermal head elements: 300 dpi

Thermal head control

The thermal head contains heating elements at a density of 300 dpi. The thermal
heating elements melt the over-coating and polyester film layers of the master, in
accordance with the image signal for each pixel.
The PSU applies power (VHD) to the thermal heating elements. The power source
varies from one head to another because the average resistance of each element
varies. Therefore, when replacing the thermal head or power supply unit, it is
necessary to readjust the applied voltage to the specific value for the thermal head.

Thermal head protection

The thermistor on the thermal head provides thermal head protection, preventing
the thermal head from overheating when processing a solid image. The CPU
checks for any abnormal condition when the Start key is pressed; it displays an
error code on the operation panel as follows:
No.
Thermal Head Overheat
E-04 The temperature of the thermal head is greater than
54 C when the Start key is pressed.
Thermal Head Thermistor Open
E-09
The thermistor output voltage is over 4.9 volts.
C231/C237/C238
292.032 mm
Symptom
6-16
Possible cause
Overheat (wait for the
thermal head to cool down)
Thermal head
Thermal head thermistor
Thermal head connector
SM