HP67 button and card reader help


To the help desk,

I bought a 67 with a gummy wheel card reader. I replaced the gummy wheel with fuel tubing off the same section of which I repaired two 97's. The 97's worked perfectly with over 50 cards without error but the 67 does not work well at all. The problem is even with the cam adjusted to max grip the card is slipping. Its not the clutch. On the 97's the cam was adjusted about 1/2 way and with the calc off its firm to insert a card, with the 67 its quite soft and the card can be pushed in easily.

Any Ideas - it seems like the 67 reader is a different beast.

Second problem is the "A" and "B" and "E" keys only work when you push the key towards the top left of the calc.

Is this a cold solder joint or just a clean?

When measuring continuity with a digital volt meter is there any danger with the cmos circuitry or is this a no no.
(I haven't tried measuring as yet)

Any help appreciated.

Thanks Malcolm



I've had this happen frequently. Simply cut a shim of "Scotch" adhesive tape and wrap it around the gear shaft for about two layers. Trim flush, and try the tubing again.

It sounds like the keyboard just needs cleaning. It's been described here: take a piece of fine sandpaper or "crocus cloth", cut a thin strip, and while pushing down on the flexible metal to make contact with the circuit board, pull the sandpaper out. Turn it over and repeat. Use a VERY fine sandpaper, and repeat a few times on each key. Should clean the contacts right up.

Let us know if these don't do the trick, and if they do!



Are you SURE it is not the clutch? The HP67 and HP97 reader drive components are the same. If it worked on the 97, it should work fine on the 67. I have seen numerous readers that worked for a few times after being reassembled, but then the shaft coupling between the motor and worm gear (what a lot of people call the clutch) started slipping. Take it apart again and give the worm gear a little tug... I bet it comes off really easily.

I have also noticed that at least one manufacturer of fuel line has recently increased the internal diameter of the line. What used to work very well is now too big for HP repairs.


Thanks Michael and David,

I did the sandpaper thing UUUGGGHHH I hated that, but it worked. I used stuff that was finer than 1200.

I think it might have been the clutch but I also replaced the tubing with a slightly larger piece. I have found around 6.2mm is good 6.1 is too small. I fixed both and now it reads / writes fine.

I'm a happy camper again.

Thanks Malcolm


The world is a better, more complete place!

Each newly working HP calculator enhances the entire universe.... by just a little bit.... not that I'm biased, or anything....

Congratulations, and

(H)appy (P)rogramming!

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