Panasonic Facsimile UF-590, Service Manual

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Fuser Roller (709)
A Teflon coated roller supplies the heat for bonding the toner to the paper. The temperature of the
surface is kept constant at approximately 160
° C (±5 ° C) or (320 ° F).
Pressure Roller (706)
This converted PFA tube Silicon Rubber Roller applies pressure to the Fuser Roller, assisting in bonding
the toner to the paper.
Thermistor Assembly (728)
The Thermistor, a heat sensitive resistor, in contact with the Fuser Roller, monitors the surface
temperature. The temperature detected is used to control the ON/OFF switching of the Fuser Lamp. It
also acts as the primary overheat prevention device. A comparator circuit on the FCB PC Board acts as
a secondary overheat protection and becomes active at approximately 185
°
C (365
°
F).
Thermostat (725)
A Thermostatic Fuse, part of the power line for the Fuser Lamp, provides an extra overheat protection by
opening when the Fuser Roller surface temperature reaches approximately 200
° C (392 ° F) and remains
there for 1 minute. If the primary and secondary overheat protection does not halt the rise in
temperature, the thermostat opens, removing power from the Fuser Lamp. When the Thermostat opens,
it must be replaced.
SNS4 PC Board (1007) [Paper Exit Sensor]
This sensor detects the presence of printed paper at the exit. If no paper passes, or if paper is over the
sensor too long, a “RECORDING PAPER JAM” message is displayed. When paper passes over the
sensor, the output is Low (Low Active).
Thermal Fuse (726)
It is placed in series with the Thermostat on the power line of the Fuser Lamp and performs the tertiary
overheating prevention (in case the Thermostat fails) by opening when the surrounding temperature
reaches approximately 216
°
C (420.8
°
F).
6.1.5 Covers and Enclosures
The Printer Cover (106) contains the R and L Document Guides (107 and 108), which adjust to the
paper width to properly feed the original documents. The Left Cover (103) has a Speaker (117) mounted
inside and shields the circuit boards. The Rear Cover (105) contains the Recording Paper Tray (111) and
Recording Paper Sub Tray (112), used to support legal size documents.