HP M750 series

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All rollers disengaged: The ITB disengages from all four photosensitive drums. This is the state during
a standby period, and also is the home position for the primary transfer rollers.
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All rollers engaged: The ITB engages with all the four photosensitive drums. This is the state for full-
color jobs.
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Only black roller engaged: The ITB engages with only the black photosensitive drum. This is the state
for the black-only print jobs.
The operational sequence of the primary transfer roller engagement and disengagement control is as
follows:
1. The fuser motor drives the primary transfer disengagement solenoid to rotate the primary transfer
disengagement cam.
2. As the cam rotates, the YMC slide plate or the Bk slide plate moves to right or left. This causes the
primary transfer roller to move up or down.
3. The ITB engages with or disengages from the photosensitive drum depending on the movement of the
primary transfer rollers.
The DC controller determines that an abnormal primary transfer roller disengagement error has occurred and
notifies the formatter. This error happens when the DC controller does not detect a specified signal from the
primary transfer disengagement switch, even though the primary transfer disengagement solenoid is driven.
ITB unit presence detection
The DC controller detects the ITB unit presence by monitoring the primary transfer disengagement switch.
The DC controller drives the primary transfer disengagement solenoid for specified times during the initial
rotation period of the following:
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The product is turned on
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The product exits Sleep mode
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The door is closed
The DC controller determines an ITB unit absence and notifies the formatter when it does not detect a
specified signal from the primary transfer disengagement switch.
ITB cleaning mechanism
The cleaning blade in the ITB cleaner scrapes the residual toner off the ITB surface. The ITB motor drives the
residual toner feed screw and the screw deposits the residual toner in the toner collection unit.
The DC controller detects whether the toner collection unit is full by monitoring the ITB residual toner full
sensor. When the DC controller determines the toner collection unit is full, it notifies the formatter. The DC
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