LJ4 jams after fuser

[InkyFingers]

Hello Folks,

My trusty old LaserJet 4 has, all of a sudden, started getting paper jams. The jams are 100% consistent, paper jams every time and in exactly the same place. The sheets get about 3/4 of the way out of the fuser and just reach the output assembly rollers and then stop. I have also tried various paper types and my usual brand is HP Laser Paper (so that ought to be OK!).

There are no paper fragments in the path. I have removed the fuser unit and there are no broken gears and the mechanism seems to be functioning normally. The output assembly also seems to be functioning correctly (and it never creates an "accordian" fold). I have tried paper both from the cassette tray and the manual feed tray and the outcome is the same.

My guess - there is a malfunctioning sensor somewhere but I don't know where.

Ideas anyone?

[MichaelTech]

There are two sets of rollers in the exit assy. These need to be replaced.
Ensure the paper setting is set to letter. Replace the P/U roller.
A timing issue may be the cause. The Pick-up assy. may need to be replaced.

[InkyFingers]

There are two sets of rollers in the exit assy.

I presume the first set of rollers are the ones clearly visible when you open the rear door? The second set of rollers are they the ones just visible above the output tray?

These need to be replaced.
Ensure the paper setting is set to letter. Replace the P/U roller.
A timing issue may be the cause. The Pick-up assy. may need to be replaced.

The P/U rollers are they the ones, as described above, visible from the rear door?

Thanks for the reply.

[Strider]

Usually with the output rollers causing jamming,the paper will be accordian folded in the last inch.It sounds to me like your exit switch is sticking.If you are looking at the rear of the printer its at the top left of the fuser.

[woodss]

Ah this is a easily problem, replace the rollers and the belt that drives the two shafts as well as the gear that is on that assembly.

and give the assembly a good clean out too.

[ooojaya]

I would take out the fuser and look inside the cavity on the left side where you will see a small gear assembly. Mostly the gears are white in color. Turn the gears with your fingers and if you see some teeth missing, you need to replace it. Sounds like it pushes the fuser gears alright but when it gets to the missing teeth, it stops turning it of course.

[MichaelTech]

Good thimking oojaya, I missed that! I still think the problem may be the output assy. He did say he checked the gears.
Another thing is the PIU may be slipping, and\or the fuser is cutting out.