Brother MFC 4550, Руководство по обслуживанию

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III –
10
2.3 Sensors and Actuators
This equipment has ten sensors: two microswitches, six photosensors and two thermisters
as described below.
Sensor name Type Located on
Hook switch sensor Microswitch Hook switch PCB
Cover sensor Microswitch Relay PCB
Registration sensor Photosensor (PC1) Relay PCB
Sheet feeder cover sensor Photosensor (PC2) Relay PCB
Paper ejection sensor Photosensor (PC1) High-voltage power supply PCB
Document front sensor Photosensor (PC1) Document sensor PCB
Document rear sensor Photosensor (PC2) Document sensor PCB
Toner sensor Photosensor (PH1) Toner sensor PCB (on the laser unit)
Toner thermister P1 Toner sensor PCB (on the laser unit)
Heater thermister __ Fixing unit
• Hook switch sensor which detects whether the handset is placed on the handset mount.
• Cover sensor which detects whether the top cover is closed.
• Registration sensor which detects the leading and trailing edges of paper, which allows
the controller to determine the registration timing and check paper jam.
• Sheet feeder cover sensor which detects whether the sheet feeder cover is closed.
• Paper ejection sensor which detects whether the recording paper goes out of the equip-
ment.
• Document front sensor which detects the presence of documents.
• Document rear sensor which detects the leading and trailing edges of pages to tell the
control circuitry when the leading edge of a new page has reached the starting position
and when the scan for that page is over.
• Toner sensor which detects whether there is toner or a toner cartridge is loaded.
• Toner thermister which detects the temperature of the toner cartridge.
• Heater thermister which detects the temperature of the heater roller of the fixing unit.
These photosensors are a photointerrupter consisting of a light-emitting diode and a light-
sensitive transistor. Each of them has an actuator separately arranged as shown on the next
page.