Protective Functions; Protective Function; Fixing Unit Failure Detection; External And Controls System - Canon LBP5050 Series Service Manual

Lbp5050 series

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Service manual (104 pages)

Table Of Contents

100

101

102

103

104

Table of Contents

Chapter 2

Speed

6/5 speed

Plain paper (75 to 90 g/m2)

(monochrome)

Thin paper (60 to 74 g/m2)

1/1 speed (color)

Plain paper (75 to 90 g/m2)

Thin paper (60 to 74 g/m2)

3/4 speed

Thick paper (91 to 120 g/m2)

Thick paper (121 to 163 g/m2)

3) Paper interval temperature control

This control is to bring the fixing heater temperature lower than the fixing temperature at paper interval to prevent the pressure roller from overheating during

continuous printing in low speed mode at paper interval.

Temperature during paper interval is changed corresponding to the distance and paper type.

2.6.3 Protective Functions

2.6.3.1 Protective function

LBP5050N / LBP5050

The protective function detects an abnormal temperature rise of the fixing unit and interrupts power supply to the fixing heater.

The following three protective components prevent an abnormal temperature rise of the fixing heater:

- DC controller

- Fixing heater safety circuit

- Thermal fuse

1) DC controller

The DC controller monitors the detected temperature of the thermistor located at the center of the fixing heater. The DC controller sets the FIXING HEATER

DRIVE (FSRD+, FSRD-) signals to inactive and releases the relay to interrupt power supply to the fixing heater under the following condition:

- Thermistor: 230 deg C or higher

2) Fixing heater safety circuit

The fixing heater safety circuit monitors the detected temperature of the thermistor located at the center of the fixing heater. The fixing heater safety circuit

releases the relay to interrupt power supply to the fixing heater under the following condition:

- Thermistor: 240 deg C or higher

3) Thermal fuse

When the temperature of the fixing heater rises abnormally high and the detected temperature of the thermal fuse is the following condition, the fuse blows to

interrupt power supply to the fixing heater:

- Thermal fuse: 226 deg C or higher

2.6.3.2 Fixing unit failure detection

LBP5050N / LBP5050

The DC controller determines a fixing unit failure, sets the FIXING HEATER DRIVE (FSRD+, FSRD-) signals to inactive, releases the relay to interrupt power

supply to the fixing heater and notifies the main controller of a fixing unit failure when it encounters the following conditions:

1) Start-up failure

- If the detected temperature of the thermistor does not reach 40 deg C within a specified period from the heater energization during the wait period.

- If the detected temperature of the thermistor does not reach 70 deg C within a specified

period after it once reaches 40 deg C after the heater energization during the wait period.

- If the detected temperature of the thermistor does not reach the targeted temperature within a specified period under the heater temperature control during the

initial rotation period.

2) Abnormal low temperature

- If the detected temperature of the thermistor is kept 100 deg C or lower for a specified period under the heater temperature control during the print period.

3) Abnormal high temperature

- If the detected temperature of the thermistor is kept 230 deg C or higher for a specified period.

4) Fixing heater drive circuit failure

- If the specified count of the ZERO CROSSING signal is not detected within a specified period after the printer is turned on.

- If the ZERO CROSSING signal is not detected for a specified period during the print period after the signal is once detected after the printer is turned on.