Last week, I repaired the HP-67 I purchased on-line about a year ago (thanks to members of this forum for the card reader advice).
This week I wrote my first HP-67 program, for computing node voltages of simple networks of one or two nodes, with inputs consisting of constant current sources, and resistors connected to voltage sources, like this:
I actually started this program about a year ago, and tested and debugged it on my HP-41CX with the card reader plugged in (for the HP-67 compatibility functions), but finally entered and saved it on my '67 this week.
I've documented my efforts at http://www.stefanv.com/calculators/hp67_resistors.html.
There's a brief section at the end of the article entitled "Possible Improvments". Since this forum loves HP programming challenges, consider it a challenge. :-)
Stefan Vorkoetter
(PS. Last time I posted a link to one of my articles, one member complained about the fact that there are ads on my site. Those ads are all in a narrow column down the left side, and help pay for the web hosting. If you're offended by ads, feel free to not drop by.)