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Repairing 9120 (and possibly other) printer platens

Posted by David Smith on 24 Jan 2006, 7:58 p.m.

The HP-9120 printer for the HP-9100A and 9100B calculators has a rubber paper advance roller (platen) . Like all things HP and rubbery the platen rubber has reverted back to its primordial goo. It is the nastiest, stickiest, black goo you can imagine.

A local surplus shop had the perfect material for repairing the platen. It is 3M Cold Shrink 8426-9 electrical connector insulator. This material is basically a rubber tube that has been stretched over a collapsable polyethylene core.

You remove the paper advance roller from the printer, measure the position of the rubber on the shaft, clean the goo off the shaft, insert the cleaned steel shaft into the core of the Cold Shrink insulator and peel out the supporting polyethylene material. The rubber insulator shrinks down onto the steel shaft. You then trim the ends of the rubber to match the size of the original roller. Voila, a REALLY nice paper advance roller. The resuting platen exactly matched the original diameter.

The Cold Shrink rubber material has a VERY grippy texture with just the right amount of "give" to it. Paper will NOT slip on the stuff.

DigiKey sells the stuff for $16.16 A nine inch piece can do two rollers. An 11 inch piece ($19.36) should do three rollers.

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