HP41C On Button Oddity / Help please

[mfleming]

Per Monte's comment, the flex circuit (my avatar, btw) has a contact resistance on the order of one or two ohms max. Pretty close to the original wire wrapped zebra contact I would guess. The Buna-N cord that separates the flex halves does have a similar failing to the Pioneer and later model keyboard sponge that compress over time. I found if you open an HP-41 with a flex connector, you need to roll the cord between your fingers to return it to its circular shape before closing the case back up. You often need to do the same with the elastomeric pads anyway, plumping them up when the connection gets dicey.

Sorry to say twoweims, the last of the flex have been sold. I was surprised to get the query about them, given the last sale was about this time in 2017. If others are interested, I could post the Gerber files for anyone who'd like to replicate the flex circuits. Keep in mind though the minimum order amount would total around $100, so it's not practical for just one person to make some. There would be enough produced though (20~25 in a min order) that you could arrange a group buy to spread the cost around.

One other thing has changed in the intervening three years; national post offices have become very picky about what constitutes a letter versus a package. That has increased U.S. and International First Class postage by about a factor of three if the Buna-N cord is included! The postal clerk now checks any envelope I bring in for PCBs or other non-paper content when she sees me come in

~Mark