HP LaserJet 4

There are also PostScript variants of these machines with the '4M' designation, where M stands for, but is not limited to, usage with an Apple Macintosh.

Hewlett-Packard dominated the laser printing sector during this time in part due to their reliability, relatively affordable pricing, and the spread of LaserJet 4 models from personal use up to heavy business use.

The EX (and EX+) print engine is known for its reliability and longevity, and in comparison to earlier generations of laser printers, these machines have acquired a 'workhorse' reputation.

The heat shrink extra diameter pulls the paper quicker and resolves the wear/slip issues.

Another alternative is to use coarse quality abrasive paper such as those used by belt sanders to roughen the surfaces of the rollers.

[5] These models also feature a 20-30W power saving (stand-by) mode, which was not included in the original Laserjet 4.

The 4Si (and 4Si MX for the Macintosh) were heavy-duty business printers, produced using the Canon NX engine.

This delays the release of the solenoid, which causes the paper to start feeding slightly late.

The error accumulates with each page printed, and eventually the paper is entering the mechanism so late that the printer believes that a jam has occurred.

This problem is fixed by removing the felt pads, cleaning off the adhesive (isopropyl alcohol works well), and placing some electrical tape or other material to provide a cushion for the solenoid.

[5] Common Fixes of the LaserJet 4V and 4MV model can have accordion jam as well, caused either by a worn roller or broken tooth on the gear at the fuser door.