Musings and comments about our common interest
We have received some inquiries on whether the zebra PCB assembled requires the zebra-holder. The zebra holder piece was designed to hold the separate zebras you can find in older calculators: the golde ones, not the elastomeric ones. If you find these, it is very likely your calculator won't work when reassembling - you'll have to replace it.
When you are using our zebra, it can very well go alone, without any support. It is strong enough to keep shape no matter what:
Until now we have been using a test order of zebra PCB circuits ( Zebra PCB version 3)
We have just received the definitive version (v4) which has a slightly modified dimension to have a better fit (we're talking tenths of mm) and a more precise alignment of tracks.
All orders received this week end are already supplied with the new model
We have done more tests and now we have put it for sale: it works well. Now thinking about packaging to send them in the best way - so that the adhesive stays put until installation. Alternatives are mounting it on a lower post assembly, or another clipping method to maintain the pressure between up and down.
Further pictures on the first production run:
The HP41C full nut requires two zebra contacts betwen the keyboard circuit and the main processor. The original zebras seldon get destroyed, but in severe corrosion cases, the zebra connectors are also affected. Then you need to change them.
In HPmuseum.org there were several threads about alternatives for the zebras. We have done something else: we have custom-ordered a couple of zebra connectors that work for our application. The length, width and height are based on the originals.
Now, the original is two round copper cylingers joined by a plastic membrane. As we don't have this membrane, we have designed a "zebra-holder" that keeps the zebra pair in place. It is made in 3D printed nylon (with a HP printer, of all brands!). It replaces the old structure, so that it can be round the zebras to keep them firmly in place. The old structure can be removed with pliers and a little force. Be careful to avoid breaking the screw posts.
If the screw posts are damaged, broken, or the screw rotates freely in them, the required piece is a different one, the lower post repair, which replaces both the zebra holder and the screw post, and that is glued in place.