Repair of a HP-97 printer



#2

I need directions to repair the thermal printer on my HP 97. It prints fine but doesn't advance the paper well. the paper only goes up one-half of a line, so that the print from the next line crowds the previous entry.

Thanks for your help


#3

This is a very common problem. The rubber roller rings at the ends of the paper feed cam harden, decompose, or develop flat spots.

You can try opening up the machine, removing the printer mechanism (or the whole inner backbone assembly), and cleaning the small yellowish white rubber ends of the feed cam where they contact the paper. I have had some success using a rubber drive wheel/drive belt restorer compound. It is available at electronic supply stores. MG Chemicals or Projector Recorder Belt Company supply it. MG's smells slightly minty (methyl salicylate) and PRB's smells like finger nail polish remover.

The problem is that the fix sometimes does not last. You may need to reapply it several times over a several weeks.

Basically you wet a small brush and apply it to the roller, pull up the paper a line or two, and keep going until you have coated the whole roller a couple of times around. Then you wait a few minutes and wipe it off. Keep it off of the plastic feed cam, etc. It softens and disolves plastic.

The only sure fire fix is to replace the whole feed cam assembly with a known good one. The feed cam from an HP41 82143A printer works well and tend to be less likely to be bad than an HP91/92/97 cam. Removing and replacing the cam assembly is a REAL pain. Lots of fiddly small parts and the chance of cracking the print head await.


#4

You can also try using isopropyl alcohol on the end of a Q-tip, it does a really good job in most cases. The other common problem is a worn idler gear (the whitish one) on the side of the printer. If some of the teeth are missing from it, you'll get an inconsistent feed. This gear can be replaced by a commercially available one (see my artcile on this in the articles forum).


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