HP-67 Card Reader became very touchy

[John Garza (3665)]

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