HP LaserJet 40X0 -- Vertically Elongated Prints

We've only seen this once, and it had us going for awhile -- it was a baffling symptom. A LaserJet 4000 was giving prints that were 'stretched out' a bit vertically. The user's application was critical for vertical registration and positioning throughout the length of a page, so he couldn't live with it.

At first, we thought it was a vertical registration (top margin) problem, but adjusting that didn't alter the elongation.

It turned out that it was caused by slightly swollen rubber rollers on both the registration assembly and the paper feed assembly. The increased diameter of the rollers increased the linear speed of a sheet of paper as it went through transfer -- hence, an elongated print.

There are probably more machines out there that have the same problem, but most applications don't reveal it.

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