HP-67 battery pack disassembly

[hansliss]

Does anyone here have a lot of experience disassembling/rebuilding HP-67 battery packs? I'm wondering what's the least destructive way to take the original battery pack apart, before I just break it open.

[vassilisprevelakis]

just run an exacto knife around the side where the top half is glued to the bottom half. In this way you can separate the two halves and gain access to the batteries.

[hansliss]

(06-10-2022 12:23 AM)vassilisprevelakis Wrote:  just run an exacto knife around the side where the top half is glued to the bottom half. In this way you can separate the two halves and gain access to the batteries.

Thanks! I suspected this was how to do it, just needed confirmation.

[GreyUser]

They are fused together by ultrasonic welding.

Place a welded end on a solid, flat surface. Place a new utility knife blade in the opposite, exposed seam. Hold blade with your non-dominant hand and wack top edge with a small hammer until the weld fractures. One or two hits is usually enough. Flip over, hold the now opened end together with a spring clamp and repeat on the remaining sealed end. Without the clamp, the halves will deflect open upon impact, absorbing the blow and it will not have the desired effect.

[hansliss]

(06-10-2022 05:34 PM)GreyUser Wrote:  They are fused together by ultrasonic welding.

Place a welded end on a solid, flat surface. Place a new utility knife blade in the opposite, exposed seam. Hold blade with your non-dominant hand and wack top edge with a small hammer until the weld fractures. One or two hits is usually enough. Flip over, hold the now opened end together with a spring clamp and repeat on the remaining sealed end. Without the clamp, the halves will deflect open upon impact, absorbing the blow and it will not have the desired effect.

Thanks! I did this, using a scalpel, a hammer (wielded with precision ) and an adjustable wrench to keep the pack in place and clamped together. Worked perfectly!

[GreyUser]

Excellent! It’s not as dangerous as it sounds, I’ve lost count how many packs I’ve opened and still have all ten digits, without scars. The method works for any HP calculator battery type that have plastic shells as they’re all ultrasonically welded.

Liquid styrene model cement (the water like stuff, Tenex or Plastruc) work really well, to re-close without any ooze or visible glue. Only takes a few small drops in either half. The stuff is great for any case or HP41 post repairs. Maybe not worth buying for one battery but who here has just one HP calculator?

[hansliss]

(06-12-2022 04:09 AM)GreyUser Wrote:  Excellent! It’s not as dangerous as it sounds, I’ve lost count how many packs I’ve opened and still have all ten digits, without scars. The method works for any HP calculator battery type that have plastic shells as they’re all ultrasonically welded.

Liquid styrene model cement (the water like stuff, Tenex or Plastruc) work really well, to re-close without any ooze or visible glue. Only takes a few small drops in either half. The stuff is great for any case or HP41 post repairs. Maybe not worth buying for one battery but who here has just one HP calculator?

Actually, I tried "rebuilding" the pack with alkaline batteries after cleaning the frame and the long contact strips, reusing those and adding a couple of brass strips cut to a suitable size - all without gluing anything at all, and it stayed together well enough to work reliably. All but one of the small tabs along the top and bottom edge stayed intact, which I think helped. This may not stay together if I throw around the calculator too much, but it's definitely good enough for desk use.

[hansliss]

2022-06-12 06.49.05 by Hans Liss, on Flickr
2022-06-12 06.49.33 by Hans Liss, on Flickr