Ricoh C249, Service Manual

Page: 370 / 486

IMAGE PROCESSING
C267 6-16 SM
6.4.5 THERMAL HEAD
Specifications
Length: 292.6 mm
Number of thermal head elements: 4068 dots
Density of thermal head elements: 400 dpi
Thermal head control
The thermal head contains heating elements at a density of 400 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. Symptom Possible cause
E-04
Thermal Head Overheat
The temperature of the thermal head is greater than
54
°
C when the Start key is pressed.
Overheat (wait for the
thermal head to cool down)
Thermal head
E-09
Thermal Head Thermistor Open
The thermistor output voltage is over 4.9 volts. Thermal head thermistor
Thermal head connector
E-10 Thermal Head Energy Pulse error
The CPU detects an abnormal ID signal from the thermal
head energy control pulse.
Thermal head connector
Thermal head
MPU
E-40 Thermal Head ID error
The CPU detects an abnormal ID signal from the thermal
head.
Thermal head
MPU
Thermal head connector
disconnected