A replacement for the HP-41 zebra connector

[mfleming]

I've finished up what I think is the last round of material tests, and have found a sample that works perfectly as an offset pressing the flex contacts against their corresponding PCB contacts.

I tested three Buna N O-ring material samples; one 2mm square with a medium hardness rating, one 2mm round with a hard hardness rating, and one 2mm round with a medium hardness rating. I had tested square material in the past without success, but thought it worth a try once more with the more accurate height dimension. The square material failed with two connectors in two calculators. At best, I could squeeze the bottom of the case and get some display segments to flicker.

Both round materials worked flawlessly, the only difference being with case closure. The medium hardness material felt just like an original CPU connector was being used, providing a tight closure with only a light tightening of the screws. The hard hardness rating material on the other hand left a paper thin gap and a sense that the case wasn't quite closed. Again though, both of the round sample materials resulted in an immediate MEMORY LOST display when the battery pack was inserted. No wobbles, no reset, no pop-it-out, pop-it-back-in.

So the medium material appears to be the winner. The material yields enough to pressure to completely seal the case. The round shape concentrates the compression force along a thin line through the connector contacts to provide a dependable connection.

Case closed (sorry, pun intended!)
~Mark