asked Jun 9, 2003 at 8:11pm
Hp HP LaserJet 5MP

HP5MP main paper tray

Some months ago I installed a paper pickup kit K34. When removing one of the wiring plugs to the solenoid, the printed circuit traces to that little board to which the socket was soldered failed. So, to repair, I wired some jumper wires to the socket. This worked fine until recently when one of my solder joints failed and the pickup solenoid was again not working. Tonight, I resoldered it, and now the pickup for tray #1 works again. However, NOW, the main paper tray does NOT work. The solenoid for tray #1 trips every time. Is there a sensor someplace that I screwed up that would make this happen?
I was browsing through the archive and I saw that Moe said that the printer would default to tray 1 without the cover. That's why I said tray #1 trips every time, because I was testing it with cover off. With the cover on, if there is no paper in tray #1, I hear no paper pickup attempt in tray #2 and the paper jam light comes on. If paper IS in tray #1, it feeds and prints properly.
by Bill on Jun 9, 2003 at 8:26pm Add comment
With paper tray 2 out, I can see the paper pickup wheel. It is not moving with an attempt to feed paper. However, if I give it the slightest push during the paper feed cycle, it will engage and go completely around.
by Bill on Jun 9, 2003 at 8:53pm Add comment
Are you pushing up on the paper tray sensor when you try and test it with the tray out? You can watch the operation with the tray in and looking at it from the back of the tray.
by moe on Jun 10, 2003 at 9:42am Add comment
OK. I will try this tonight when home.
By the paper tray sensor, which part do you mean?
I purchased the Service manual. So,
I doubt you mean the arm for tray 1, RB1-6006.
Do you mean RB1-6001 Arm, Input paper sensor?
What am I looking for when I do this?

Last night, I had the cover off and Tray 2 out. I held the cover/switch interlock down (top left) and then pressed the Test Page button. With paper in tray 1, tray 1 fed and printed OK. With no paper in tray 1, the pickup roller for tray 2 did not turn. However, if I gave it the slightest push in the proper direction, then a clutch or gear engaged and it would go around with force.

It almost looks like the existence of paper in the tray is intended to provide the proper "registration" of the pickup roller.

As I remember, when I put the printer together after resoldering the wires for the tray 1 solenoid, the first page from Tray 2 jammed at the front. I had to pull this paper out. Could this have changed the registration on the pickup roller, or broken a tooth on the gear, or is there a clutch on the tray 2 pickup assy?

by Bill on Jun 10, 2003 at 10:40am Add comment
I looked closely at the paper pickup for Tray 2. I didn't find anything that looked much like a paper tray sensor, except for the following:
The pickup roller is white plastic with a black rubber pickup pad. Concentric with the shaft of the pickup roller is a black, plastic cam-like device. It kind of looks like it was meant to hang down, but is instead pushed up and wedged into the cavity above the pickup shaft. It's wedged in tight. The cam is pushing on a part that might be a micro switch, and an arm at the top is wedged into the cavity above. It's not so terribly obvious how/what to take apart to free it, other than starting at the bottom plate and see what that exposes. Obviously, if the whole pickup assembly was removed and reinstalled, this would do it. I didn't go near this part during my earlier "repairs", so I wonder if installing the paper tray in a careless manner could wedge it like this.
by Bill on Jun 10, 2003 at 10:34pm Add comment
The tray 2 paper sensor arm is the black plastic piece that hangs down on the right side of the pickup roller. It blocks an optical sensor above it.
by moe on Jun 11, 2003 at 8:58am Add comment
It sounds like we are talking about the same piece, which in my case is wedged and immovable. I tried to pop it out, but I was afraid of breaking it. It may also be putting a side load on the shaft of the pickup roller, which may be what is causing it not to engage by itself. It looks like there are a couple of springs on some white parts that are there to register the pickup roller. If I use my finger to start the roller during the feed process, it engages and takes off for a 360 degree rotation. Then this repeats a second time, them the paper jam light comes on.
How is the pickup assy removed and reinstalled? It was not entirely evident from visual inspection nor from the exploded view. I'm sure its easy once you know what to take off (and not).
by Bill on Jun 11, 2003 at 9:54am Add comment