Ricoh C211 Service Manual page 435

9-3. Temperature Ascent Detection of Thermal Head/Power Supply: SS830
A thermistor located on the thermal head and a thermal guard located on the power
supply board are used for thermal protection. This is to prevent the temperature of the
thermal head and the power supply
ing a solid image.
Thermal head detecting temp.
Thermal head return temp.
Power supply detecting temp.
board from overheating when continuously process-
55°C
49°C
85°C
When the thermistor is open, a detection signal is applied.
Thermal Head
Drive Board
<
CN708-2
CN708-1
!
Thermal Head
CN707-1OI
1
m
CN705-5
Thermal
Guard
—
Psu J
I
Master
Processing
{ CN404-
10
CN402-
12
Main Control
Board
ICN102-12
The thermal head temperature detection signal is applied if CN708-I becomes greater
than 2.53 volts (Thermal head detecting temp--- 55"C).
Note: Thermal head temperature detection signal is applied if the thermistor is open.
The thermal head temperature return signal is applied when CN708-I becomes 2.26
volts (Thermal head return temp--- 49"C).
The thermal guard detection signal is
ing temp--- 85"C).
The thermal guard temperature return
applied if CN705-5 is O volt (Power supply detect-
signal is applied when CN705-5 becomes 5
volts.
When the temperature ascent signal is applied CN707-10 goes HIGH.
When the temperature ascent signal is applied during master processing, master
processing continues until completion. The machine stops after the master making
process is finished.
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