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The 7470a plotter has two wedge-shaped gummy wheels located over the two abrasive wheels which move the paper back and forth. One of my gummy wheels has developed a flat spot in it. This causes quite a bit of chatter when the paper is being moved back and forth.

Has anyone here repaired one of these before? Is the wedge shape critical or will a straight cylinder work?

Thanks,
Andy

The paper drive wheels in the HP97, etc also develop flat spots. A little careful work with some sandpaper can work wonders in getting them going again.

From an article I believe I read in HP Digest a long time ago, the tapered roller shape is designed to keep the paper taught and against the guide at one side.

So, I would attempt to maintain/reproduce the shape as much as possible, although the overall diameter may not be critical.

If the flat spot is a result of leaving the roller pressure engaged for a long time, perhaps it will improve a bit after some relaxation and use.

If you find/develop a good replacement, please let us know.

Good luck!