Gummy Wheel Repair for HP-97

[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