Canon LBP1760P, Service Manual

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F. Paper Jam Detection
The following paper sensors are installed to detect whether the paper is present or not and
whether the paper is fed normally or not.
•
Pre-feed sensor (PS102)
• Top of page sensor (PS103)
• Fixing unit delivery sensor 1 (PS501)
• Fixing unit delivery sensor 2 (PS106)
• Envelope multiple feed sensor (PS902 in optional envelope feeder)
The microprocessor (CPU) determines whether paper is jammed or not by checking whether
paper is present or absent at the sensors at check timing stored in the memory.
If the CPU determines that a jam has occurred, it stops print operation and notifies the jam
to the video controller.
1. Pick-up delay jam
a. When picking up paper from the cassette
The CPU assesses a pick-up delay jam if the pre-feed sensor (PS102) does not detect the lead-
ing edge of the paper within the prescribed period of time (T) after the paper was picked up, or
if the top of page sensor (PS103) does not detect the leading edge of the paper within the pre-
scribed period of time after re-feeding.
•
In case the paper is picked up from the cassette: T= about 3.2 sec.
• In case the paper is picked up from the paper feeder: T= about 4.6 sec.
b. When picking up paper from the multi-purpose tray or the envelope feeder
The CPU assesses a pick-up delay jam if the top of page sensor (PS103) does not detect the lead-
ing edge of the paper within the prescribed period of time (T) after the paper was picked up.
•
In case the paper is picked up from the multi-purpose tray: T= about 7.5 sec.
• In case the paper is picked up from the envelope feeder: T= about 5 sec.
2. Pick-up stationary jam
a. When picking up paper from the envelope feeder
The CPU assesses a pick-up stationary jam if the envelope multiple feed sensor (PS902) detects
multiple envelopes after the envelope pick-up operation.
b. During paper feeding
The CPU assesses a pick-up stationary jam if the top of page sensor (PS103) does not detect the
trailing edge of the paper within the prescribed period of time (about 4.4 sec.) after detecting the
leading edge.
c. During paper feeding
When feeding a regular sized paper (A4, Letter, Legal, B5, Executive), the CPU assesses a paper
stationary jam if the paper length in the vertical scan direction detected by the top of page sen-
sor (PS103) is 250 mm or less.
d. When WAIT period starts
The CPU assesses a pick-up stationary jam if the top of page sensor (PS103) detects paper when
the WAIT period starts.
3. Delivery delay jam
a. During paper feeding
The CPU assesses a delivery delay jam if the fixing unit delivery sensor 1 (PS501) does not detect
the leading edge of the paper within the specified period of time (T) after the top of page sensor
(PS103) detects the leading edge of the paper.
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CHAPTER 2