HP-67 Card Reader became very touchy

[Alevin]

(10-17-2023 01:23 PM)John Garza (3665) Wrote:  Part of the card reader refurb is to replace the clutch. Pull the worm gear off the motor shaft, and dig out all remaining clutch material inside the little cup at the end of the worm gear. Fill with RTV sealant or gasket maker, insert the motor shaft, ensure it is straight (the shaft mates with a hole at the bottom of the cup) and let dry overnight. Also square profile O-rings seem to be the best replacement for the card reader drive roller. It used to be model airplane fuel line, but production of that has moved overseas with lower quality control (as in concentric inner and outer radii). Circular O-rings have less gripping surface and seem more prone to smear pencil marks on the card face along 2 parallel lines.

HP topcat printer gears can be found on the auction site. I've replaced many over the years, they work fine. The metal ones are 'freshly minted' and can do with some wire brushing to remove sharp edges and burrs. I lube with moly-di, same as the card reader worm gear for smooth operation. While you are in there you should also remove the paper advance rollers (both ends of the shaft) as they become brittle and slick with age. Once cleaned of all the remaining roller bits, just slip on some tight fitting silicone/rubber tubing cut to size. Works great. And you can also clean the print-heads with IPA. They rarely get such an opportunity for a thorough cleaning.

It may seem daunting at first, but once you do one, the fear will subside. Be careful of the little springs flying away if they are under tension.

-J

Thanks a lot for your recomendations.

I tried in an Hp-65 clutch repair with the silicone procedure, but I got troubles in getting the ensemble engine staff-worm aligned.

In respect idle gear, I made a previous repair in another HP-67 with a bronze gear, and my experience was not quite satisfactory. Expanding the bore to the right size an keeping well centered was not a straightforward task with my simple tools. Then it had tendency to wobble, and move back an forth over the axe, as the width is smaller than the original and the circaclip is away from the outmost external face. It causes some time to get stuck in diagonal in between the motor pinon and the printer gear, . Finally, it was really noisy.

That is why I am going to attempt now with a printer plastic one. Shapeways nowadays offers more printing materials to try. I will document the experience in the threat.


I am grateful for your encouragement to go ahead with the full printer repair, but still I am apprehensive. I have study the theory and maintenance manual, and It seems the printer paper avance rings are not easy to replace. As previous to the idle gear collapse they did the job well, unless I can detect that the printer head stuck comes from them (May be some one got broken?), I am keeping them as they are, by the way. It is a collection item, just for exhibition, trying to keep in working order, but not intended for every day desk work.