HP 3150 EN - Manual (Page 79)

EN Printer feed system 77
Printer feed system
Both the paper input bin and the single-sheet input slot merge into
one, main input area. Paper placed in either of these areas enables
the paper-out sensor (PS202), which informs the ECU that paper is
present.
When the printer receives a print job and is ready to print, the ECU
enables the laser/scanner assembly and the motor. Paper motion
begins when the ECU energizes solenoid SL1. This causes the paper
pickup roller to rotate once. Two actions occur as a result of this
rotation. First, the paper kick plate pushes the paper against the
pickup roller. Second, the pickup roller grabs the top sheet and
advances it to the feed assembly drive rollers. To ensure that only one
sheet is fed, a main separation pad and two subpads hold the
remainder of the stack in place.
The feed assembly drive rollers advance the paper to the paper
registration photosensor (PS203). This sensor informs the ECU of the
exact location of the paper's leading edge, so that the image being
written on the photosensitive drum can be precisely positioned on the
page. The feed assembly drive rollers then advance the paper to the
transfer area where the toner image on the photosensitive drum is
transferred to paper.
After the image is transferred, the paper enters the fusing assembly
where heat from the fuser and pressure from the pressure roller
permanently bond the toner image to paper. The paper exit sensor
(PS201) determines that paper has successfully moved out of the
fusing area. The fusing assembly exit rollers deliver paper to either
the paper output bin or the front paper output slot, depending upon
the position of the face-up/face-down lever.