HP Laserjet 4000 paper jam and other issues.

Replace the feed roller RB1-8865 located above tray 2. If my guess(tm) is correct, the printer has never had any of the rubber parts replaced. Considering it's age, you might as well replace ALL the rubber. Cheap enough:

Congratulations. Your printer also has the HP exclusive sticky solenoid problem. How to fix it on an HP2200, HP2300, HP4250, etc. Unfortunately, I haven't bothered to make a web page for the HP4000 series printers. It's similar to the others except that the solenoid is buried under additional layers of metal plates. I suggest you take photos to help with the reassembly. Tear the printer apart. Find the sticky solenoids. Clean off the sticky goo from BOTH the armature and solenoid core using solvent. Apply thin felt as shown. Demagnetize the solenoid core if you suspect that it's magentized. Put Humpty Dumpty back together again. Be sure to thank HP for ignoring the problem since the earliest HP laserjet printers.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 

Hi Jeff,

I did clean (though probably not well enough) the sticky stuff off of the solenoid which is used to control the lower "D" rollers. I used some electrical tape as was suggested in the fix. Is the purpose of the felt or electrical tape to muffle the sound when the solenoid is energized or is there a mechanical reason as well? I'll take it out again, put some dc on it, and see how it operates. I'll also replace the rubber parts.

Thanks for your reply.

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David Farber 
Los Osos, CA

Don't use electrical tape. My original version of the fix indicated to use 2 layers of electrical tape. That worked for about 3 months, when the tape got warm and fell off. I had to rework about 8 printers where I had used tape. The felt has lasted much longer.

There are various thicknesses of felt available at the local hardware store. The stuff in the photo is 2mm thick (including the backing paper and NOT compressed). I also have some felt that's about 1mm thick. Both work just fine but I would NOT go any thicker than 2mm.

The main purpose of the felt to reduce the sound, but it also may have a secondary purpose. Running the solenoids off DC tends to magnetize the cores. If the armature comes in contact with the core, it will stick. See video at: The felt provides the necessary air gap so that the armature doesn't stick.

If replacing all the rubber parts and fixing the sticky solenoid doesn't do the trick, there are some obscure problems that should be investigates. The clutch that runs the feed roller (the one above the paper tray) gets dirty and doesn't release. Tear it apart, clean out the metal dust, and it should be ok. Another common problem is a sticky paper height sensor. That's also above the tray. Clean with a paint brush.

Good luck.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 

Hi Jeff,

I purchased the package of felt you suggested (picture at the bottom of this page

and put it on the solenoid. It was just the right thickness to allow the relay to close. However after reassembly, the printer still was spitting out blank pages. In other words, the solenoid somehow was not releasing. I did some more web searching and finally found a link to the step by step procedure to do the repair. Long story short, I finally realized I had pulled the wrong solenoid. The one I was working on was for the upper tray #1, not tray #2 (the drawer that slides out). I went back to the service manual and figured out how to get access to that solenoid. It was stuck shut of course. I removed the stickiness from the components and put the felt on. For some reason, this solenoid would not close when I manually tried to close it. The felt was too thick. I removed the felt, put some electrical tape on it, and now it works great. As for the electrical tape, if it fails again, at least I know exactly where to find that solenoid. If anyone is interested, what follows below is a very concise list of steps you can follow to get somewhat easy access to the solenoid on the 4000 model.

Thanks for your help.

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David Farber 
Los Osos, CA 

Oops. The URL I supplied was for the Tray 1 solenoid.

Hmmm... That's odd. I've been using the 2mm thick felt for HP solenoids without difficulties. There is a solenoid in the HP2550n color laser that requires 1mm thick felt, which I was able to find at the local $1 store.

The neighboring office has an HP4000 that is going to the recyclers shortly. I'll take a closer look at the solenoid (time permitting).

If my experience is any indication of future performance, the glue will either melt or evaporate. Old electrical tape becomes brittle and non-sticky after a few years. Either way, I believe that the electrical tape will eventually fall off. I predict you'll be digging in again in a few months.

Did you check for a magnetized solenoid?

Thanks. I'll plagiarize it for when I eventually do an HP4000 instruction page.

Congrats and sorry for the confusion.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com