Printronix L1024, Maintenance Manual

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13–39 Chapter 13 – Troubleshooting Guide
Follow the procedures for fuser testing in Chapter 7,
Fuser Subsystem. These procedures are
very helpful in learning how the fuser works and in determining what component is at fault.
Look through the cooling holes in the rear of the top cover of the printer to see if the lamp is lit
during the warmup cycle. This will help to isolate the problem.
If the fuser is underheating and does not reach the correct temperature in a fixed amount of
time, an error will occur. If the fuser overheats, it will cause the thermal breaker to trip, and the
lamp will not light at all.
a. Follow these steps if the lamp is lit during the warmup cycle:
1) Make sure the thermistor does not have excessive toner buildup on it, which
will cause overheating. Clean or replace the thermistor.
NOTE: In a normal overheating condition, the thermal breaker will trip when the
fuser temperature reaches the tripping point of the breaker. When there is
toner buildup on the thermistor, the temperature will exceed the breaker’s
trip point, and the breaker will trip. This stops the flow of current to the
lamp, and the fuser will no longer heat.
2) The thermistor itself is not functioning correctly, and must be replaced. It may
be intermittent, or it may be sending erroneous information.
3) The Digital-to-Analog converter for the thermistor is faulty. The Engine
Controller Board must be replaced.
4) The reference resistor on the fuser sensor board is faulty. This resistor sets the
reference voltage for the desired fusing temperature. The fuser sensor board
must be replaced.
5) The Data Controller Board is requesting status from the Engine Controller
Board too often. The Data Controller Board is requesting status information
from the Engine Controller Board at a rate faster than once every 10 ms (may
vary depending on the controller). The Engine Controller Board does not have
time to perform the Digital-to-Analog and Analog-to-Digital conversions for the
fuser temperature circuitry. The Data Controller Board must be replaced.
b. Follow these steps if the lamp is not lighting:
1) The thermal breaker has tripped due to an overheat condition. Remove the
breaker, measure its resistance, and replace it if it is open (infinite resistance).
2) The lamp is open or broken. Check its resistance to see if it is open, and
replace the lamp if its resistance is more than 2 ohms.
3) Fuse F2 is blown in the L.V.P.S. This prevents 110 V (or 220 V) from being
supplied to the lamp.
4) The thermistor is faulty and must be replaced. Disconnect its cable from the
fuser sensor board and measure its resistance. Make sure the thermistor is
not open.
5) The Fuser Sensor Board is faulty and must be replaced.
6) The Digital-to-Analog converter is faulty and the Engine Controller Board must
be replaced.
28 BEAM DET FAIL—Call Service
1. A beam detect failure has occurred. This means that the LSU motor is spinning, but it is not
generating interrupts.
a. Check the wiring to the LSU. Repair any wiring problems found.
b. Replace the L.V.P.S.
c. Replace the LSU.