Gummy Wheel Repair for HP-97

[John Cadick]

I have an HP-97 that I believe has gummy wheel. Everything works except cards won't feed. Does anyone besides fixthatcalc do this kind of work? I could probably "tear" into it myself, but I'd much rather pay somebody that knows what there doing -- you know -- somebody that has been there, done that, and has the t-shirt.

[Paul Berger (Canada)]

You could try http://www.vintagecalculatorrepair.com/

[Brad Barton]

John,

I had the same trepidation on my 97, but after a quite a bit of research, I went ahead and dove into it. It was not nearly as bad a job as I thought it was going to be. The 97 opens up very easily, and some of the instructions I found on line were quite detailed. I also fixed the printer feed while I was in there, and everything came out beautifully.

I took a lot of pictures as I was disassembling it, and they came in hand on the way back together. Just be sure and have a clean work area, and use a ground strap because some of the chips cannot be found anywhere. In fact I've got a spare 97 that works perfectly, but the battery went bad. I'm pretty sure that the ACT chip got blown the next time it was plugged in and it's been sitting ever since.

Don't let that discourage you though, the gummy wheel repair isn't that difficult with a bit of care.

[Duane Hess]

There is another repair service. Check the user 'plasmoid' on TAS. Forget his name, but he is on here. Of the several postings (somewhere on this site) about card reader repair methods, he is one of the batch.

Not trying to suggest this guy versus anyone else, simply know of his services. You might have to message him about repairs, as his postings often have only 41C in the title.

[Dale Reed]

(03-19-2014 03:38 AM)Brad Barton Wrote:  I took a lot of pictures as I was disassembling it, and they came in hand on the way back together. Just be sure and have a clean work area, and use a ground strap because some of the chips cannot be found anywhere. In fact I've got a spare 97 that works perfectly, but the battery went bad. I'm pretty sure that the ACT chip got blown the next time it was plugged in and it's been sitting ever since.

Don't let that discourage you though, the gummy wheel repair isn't that difficult with a bit of care.

I did the O-ring fix on my HP-67. All that about work area, grounding, and taking pictures is absolutely great advice. I also printed all the pictures from the article I found online and checked them off one by one as I went.

Finally, have a LARGE, level work area with a border. There are four little white plastic balls that love to roll away, never to be seen again, and two little springy clips that are remarkably aerodynamic! Oh, and no pets! I have four cats, and keeping pet hair away (and paws, for that matter!) is a must!

If you can use a big table and have one of those old 3M static-safe work mats you can put on it, plus a lighted magnifier, it's a piece of cake. A muffin tin to store screws and such as you remove them (1st muffin = disassembly step 1 hardware, 2nd muffin = step 2 hardware, etc.) is a great way to get the right parts back in the right place.

Heathkit had a separate "how to build a Heathkit" (not the title, but the intent) book that went over parts sorting and tracking, tools, soldering, resistor color code, etc., etc.) that they shipped with their kits near the end of their run. (This book came with a kit I got in 1974 or 1975, I believe.) Wish I had a copy. If you find it, get it. Lots of good advice, even just for repair rather than kit-building.

I say go for it. Plan a time, avoid distraction, concentrate, work in a comfortable, well-lighted space and you'll do ABSOLUTELY fine. And if you need help, just ask back here!

Dale