HP-97 Card Reader Repair Adventure



#2

As I half-expected, repairs to the printer (see http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv021.cgi?read=221088#221088 if you are having paper feed problems for another (and so far very successful) repair option) have led me to the next problem, a non-functional card reader. I did find some info on this and highly recommend one read through the clutch repair procedure found here (http://www.hpmuseum.org/repclutc.htm) for many important details about this mechanism. In my case the gummy wheel was completely gone and the clutch was also defective. I did repair the clutch per this guide with the exception of using some flexible Loctite Super Glue Ultra Gel Control instead of the 100% Silicone. I didn't do quite as much breakdown to the worm gear as the coupling-to-gear joint seemed fine. I just filled the motor end of the aluminum coupling with SG and pushed it on to the motor shaft. Then I quickly mounted everything to make sure I had it in the correct position. As it turns out I was slightly off and the glue had already set so I was forced to add some shims between the motor and the mounting bracket (approx. 0.006") to compensate. This may be a good reason to use the 100% Silicone instead! But all's well that ends well and at this point the motor and worm gear were working just fine.

The next step was the wheel itself and I did find several solutions posted on the Internet. One was the "O" ring set and another was the 'pink' tubing referred to in the clutch repair article. Before ordering anything or traveling 30 miles to the nearest hobby shop I decided to try Ace Hardware. There I found some small "O" rings (0.25" OD, 0.125" ID), some pink fuel line and one other clear fuel line slightly larger in OD than the pink version. This is not to be confused with the clear Vinyl tubing they also sell which is much stiffer and has a thinner wall. I first tried the "O" rings and I admit they looked perfect at first glance. They did feed the card but I noticed only one was actually doing all the work and it also had a tendency to wiggle off the shaft almost immediately. So, if it was to work, it would need to be glued in place at the very least. But before doing that I tried the pink tubing. It did have a nice snug fit to the shaft but turned out to be slightly too small in OD to work. Lastly I tried the clear version. It also had a decent fit to the shaft and had a larger OD as well. This turned out to be the best solution as it had greater surface area contacting the card and, with the adjustment screw set so the slot was perpendicular to the card path (pip towards motor), card feeding was extremely smooth. I did remove the gear one more time and put a tiny amount of SG on the shaft to better secure the new tubing and so far it has been working very well. The feed is smooth and I can't see any deviations in the feed rate by eye. I have also done some minimal testing reading and writing data with no errors so far. I don't have any preprogrammed cards but might try to find a few (cheap) just for testing purposes. I also plan to do some larger programs or data arrays to verify proper operation.

So, for next to nothing in cost, there is another possible solution for all you folks who have one of these beautiful old machines with card reader problems.

Now I have noticed that some keys are not being detected correctly so it looks like I'm going back in for the next(and hopefully final) adventure. Hopefully a little keyboard contact cleaning will be all that's required.

LHH


#3

Quote:
Now I have noticed that some keys are not being detected correctly so it looks like I'm going back in for the next(and hopefully final) adventure. Hopefully a little keyboard contact cleaning will be all that's required.

It has been some years but as I recall the 97 keyboard keys merely press down on a contact on a PC board. Hitting the contacts with some zero residue contact cleaner should do the trick. It went very smoothly the last time I did it.

Congrats, BTW, on your card reader repair. It's a rite of passage.


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