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SAFETY AND IMPORTANT WARNING ITEMS
S-12
2. Fixing upper lamp /1 (L2), Fixing upper lamp /2 (L3), Fixing lower lamp (L4) overheating
prevention circuit
2.1 Protection by software
The output voltage from fixing temperature sensor /1 (TH1) and fixing temperature sensor /2 (TH2) is read
by the CPU. If this voltage is abnormal, L2, L3, and L4 are turned OFF by opening main relay (RL1).
CAUTION:
• The clearance between the fixing upper roller and TH1 and the clearance between the fixing
lower roller and TH2 must not be changed. When replacing them, make sure to comply with the
specified clearances.
• The RL1 function must not be deactivated under any circumstances.
2.2 Protection by the hardware circuit
The output voltages from fixing temperature sensor /1 (TH1), fixing temperature sensor /2 (TH2), fixing
temperature sensor /3 (TH3), and fixing temperature sensor /4 (TH4) are compared with the abnormality
judgment reference value in the comparator circuit. If the output voltage from TH1, TH2, TH3, or TH4
exceeds the reference value, L2, L3, and L4 are turned OFF by opening RL1.
CAUTION:
• The clearance between the fixing upper roller and TH1 and the clearance between the fixing
lower roller and TH2 must not be changed. When replacing them, make sure to comply with the
specified clearances.
• Periodically check the contact between the fixing upper roller and TH3 and the contact
between the fixing lower roller and TH4, and replace them if any abnormality is detected.
• The RL1 function must not be deactivated under any circumstances.
2.3 Protection by thermostat /1 (TS1) and thermostat /2 (TS2)
When the temperature of the fixing upper roller exceeds the specified value, TS1 is turned OFF, thus inter-
rupting the power to L2 and L3 directly. When the temperature of the fixing lower roller exceeds the speci-
fied value, TS2 is turned OFF, thus interrupting the power to L4 directly.
CAUTION:
Do not use any other electrical conductor in place of TS1 and TS2.
Control
section
AC driver
section
TS1
PRCB ACDB
TS2
L2
L3
L4
RL1
RL1
TH1
TH3
TH2
TH4
FHCB
8050sf002e