HP 8550 Service Manual - Page 309

Pick-up feed system The side HCI out-of-paper sensor (PS3) detects whether or not there is paper in the side HCI. When the pick-up start signal is transmitted from the printer formatter, the deck controller PCB starts turning the pick-up motor (M3). This action causes the pick-up roller (callout 1), feed roller 1 (callout 2) and separation roller (callout 3) to turn. At the same time as the pick-up motor starts turning, the pick-up solenoid (SL1) (callout 4) goes on. This causes the pick-up roller to be lowered to the paper surface. As a result, the paper is fed to feed roller 2 by the rotating pick-up roller. When the leading edge of the copy paper reaches the feed sensor (PS5) in front of feed roller 2, the feed motor starts to turn and the paper is fed to the copy module main unit. When the deck controller PCB detects that the currently picked up sheet is the last sheet during continuous printing when the second sheet detection sensor is off, before the next pick-up operation starts, the deck controller PCB notifies the printer formatter that there is no more paper. 2 1 3 4 Figure 190. Pick-up feed rollers EN Side HCI 307