Printronix L1024, Maintenance Manual

Page: 132 / 372

7–36 Chapter 7 – Fuser Subsystem
Then, to measure the fuser temperature, use a temperature probe. Let the printer cool to ambient
temperature, then open the printer cover and defeat the cover interlock switch.
WARNING: When you defeat the cover interlock switch, there is 115 VAC at
various parts of the power supply and high voltage at other
contacts—so BE VERY CAREFUL.
Defeat the following sensors:
S
OPC drum switch (if the OPC drum is not installed)
S
Paper empty at the front of the printer
S
Top of form sensor at the fuser assembly
Flip the exit paper guide out and away from the printer. Turn on the printer. Be extremely careful of
moving parts. In about 120 seconds, the fuser roller should come up to proper temperature. The
temperature of the fuser roller should be about 185
°
C (change it, if necessary, using the control panel)
and the temperature range about 5
°
C. If not, check the position of the thermistor. It should be mounted in
contact with, and parallel to, the fuser roller. If the position of the thermistor is correct, you should replace
either the thermistor or the engine controller, or clean excess toner off of the thermistor.
Paper Positioning Section
The paper positioning section consists of a clutch and a stepping motor that has reduction gears attached
to the driving end to increase the torque of the motor. Without the gears, a much larger motor would be
required.
Troubleshooting the fuser drive motor is fairly straightforward. The motor rotates and the clutch is on until
the pressure roller is in its initial position during initialization of the printer (if the pressure roller is not in its
initial position) and after it acts according to print requests. If there is data to be printed, the motor and the
clutch are activated and the fuser is cantilevered against the pressure roller. During printing, only the
motor is activated. After the data stream stops and the print cycle is finished, the motor and clutch are
activated, which releases the fuser from the pressure roller. When the FORM FEED button is pressed,
only the motor cycles. When the motor is in position, it is locked with a detent torque.
Fuser Fan Troubleshooting
The fuser fans cool the ends of the pressure roller. During narrow forms printing, the paper (or label) stock
dissipates heat in the center of the pressure roller. The areas of the roller without paper expand and
cause the stock to move slower through the fuser.
The fuser fans also cool the end of the heat roller during narrow forms printing. If the heat roller stops, the
thermal breaker (thermostat) senses an overtemperature condition. The breaker will then open, which
removes power to the heater lamp.
The fans are powered by the switched 24 volts supplied from the engine controller board connector J5, to
the fuser sensor board connector J1. Connector J1 sends the 24 volts directly to the fans through
connectors J2 and J3.
The fuser fans activate only when the heat roller temperature is at fusing temperature, as set from the
control panel. Check that the fans are activating when the heat roller is at fusing temperature.
Remove the fuser heat shield and fuser front paper guide. Watch the fans during the printer power up
sequence to verify that they are working. If they are
not working, check for 24 volts on the fuser sensor
board, connectors J2 and J3. If 24 volts is not present at these connectors, check for a loose connector at
J1.