The HP colour LaserJet 4600s paper pickup assembly is an important component designed to pull paper through the path of the printer. Issues with this part can result in paper jams if the paper doesn't reach certain sensors in a certain amount of time. Print quality issues can result if the paper reaches the imaging process before or after it is supposed to do so. Fortunately, even for the end-user, this part is not difficult to remove or replace.
Remove the 2 screws on the rear cover. These are located on the upper part of the rear cover on the rear side of the printer. Slide the entire cover to the left to remove it.
Lift the top cover and remove the fuser by unscrewing the blue thumbscrews and lifting it straight out of the printer. Using the pliers, pinch the white clip located on the left side of the top cover (it's located on the left arm of the cover). Pop the tab and remove it from the right side of the cover, and then the top cover to the left, to remove it.
Remove the three screws that you can now see with the top cover removed. One is located on the raised plastic portion on the right, and if you follow the plastic to the left, you will see the other two. Use your flat blade screwdriver to disengage the tabs between this cover and the right-side cover. This is where the top-rear cover and right cover meet on the right side of the printer. Do the same for the left side to remove the rear top cover.
Open the front cover and look towards the left side. Remove the screw, and disengage the tabs to release the left cover. Tilt the left cover to remove it easily.
Pull each toner cartridge out of the front of the printer and set aside. Locate the blue tabs on each side of the transfer unit attached to the front cover. Disengage both tabs while slightly pulling on the transfer unit to release it.
Locate the DC controller shield on the left side of the printer toward the back. Remove the nine screws securing it to the printer. There are 10 on some of the newer configurations of this printer. If this is one of those, remove the tenth screw as well. Pull out the DC controller shield. This exposes the DC controller board. Remove the connector, two connections down from the sticker on the board. You can be sure this is the right connector by following the wire to an extremely large hole down and to the right on this side of the printer. Once you have the correct connector, push the wiring and connector through the large hole.
Locate and remove the two screws for the paper pickup unit at the front of the printer. They're located on each side of the part and secure it down into the base of the printer. Lift the paper pickup unit up and pull towards you to remove it from the printer.