Panasonic KX-FLB758RU Service Manual page 200

KX-FLB758RU
T0: Initial Temperature (At Power OFF / Normal Temperature)
T1: Primary Stable Temperature (Heater Disconnection / Thermistor Loose Connection Detection Temperature)
T2: Secondary Stable Temperature (Paper Feeding Permission Temperature / Fixing Control Temperature)
Th: Abnormal High Temperature
t0: Initial Time (After Printing Signal Received)
t1: Primary Stable Time
t2: Secondary Stable Time
t3: Paper Feeding Permission Time
tl: Abnormal Low Temperature Detection Time
tf: Fixing Stable Time
2. Safety Control by Hardware
Considering the heater remains ON due to such as a program runaway or a thermistor breakdown, the following safety devices
are prepared.
a. If the temperature detected by the thermistor exceeds 220°C, IC610-7pin becomes Low, and the heater is turned OFF
forcibly.
b. If the temperature of the thermostat exceeds 135°C(*), the internal switch turns off to cut off the current to the heater, and
the heater is turned off.
c. If the temperature of the thermo fuse exceeds 118°C(*), the internal switch turns off to cut off the current to the heater, and
the heater is turned off.
* Thermo stat and thermo fuse is apart from heat roller, so the detect temperature is low.
3. Safety Control by Software
a. Abnormal Low Temperature Detection (Heater Disconnection Detection / Thermistor Loose Connection Detection)
After the heater is ON, if the temperature of the fixing part does not reach T1 until tl, the heater will be OFF due to the
abnormal low temperature detection (heater disconnection / thermistor loose connection).
b. Abnormal High Temperature Detection
If the thermistor detects the temperature Th, the heater will be OFF due to the abnormal high temperature detection.
Temperature [°C] Register Value [KΩ]
125
180
225
Voltage [V]
20.6
7.0
3.4
200
2.2
1.5
1.0