
The board takes a CR2025 and I only had a thinner battery. With a few keys in the bottom right corner, I could power on and do a few quick calculations with no problem. One switch was a little bent out of shape but there was an extra, so I didn’t bother trying to unbend it. However, they can pop out, so I suggest doing a column or two at a time. Luckily, they have little legs that spring into the holes, so it isn’t very hard. There are 39 little tact switches to install. Switches With 39 switches, you need 156 solder joints… It did - or, at least - it powered up and said MEMORY LOST. Once I had everything but the switches done, I powered up to make sure it all worked.

The instructions, if you read them, do mention this.
#Hp wp 315 rpn scientific install
I wondered if you should install them on the back of the board, but the pictures showed them front-mounted and you realize pretty quickly you have to bend them down to let the LCD sit flat. Several components go under the LCD display and that is soldered in, so you need to put them in first. Note components squashed down for the LCD. All the parts are marked on the silkscreen and you can probably figure it out - with a few caveats. They aren’t much and I didn’t realize they were until after completing the board, but it isn’t hard to figure out. Turns out the last part of the bill of materials is a link to some instructions. There was a bill of materials, but - I thought - no instructions. Tearing into the bags was a bit frustrating, but not hard and it did keep everything separate. The components were all nicely bagged and marked. The kit arrived on the Saturday after Thanksgiving, I decided to tackle it while waiting for some 3D prints. The black Friday sale on Tindie sealed the deal for me.

Sure, I have great emulation on my phone and I use that too, but the PX-41C kit looked fun, and with all through-hole parts it would be a quick build. It has enough wear from the daily use it received 40 years ago. It is still a workhorse but at 43 years old or so, I don’t like to leave it hanging around or near anything that might damage it.
#Hp wp 315 rpn scientific serial
I still have my original HP-41C from 1979 (a very low serial number). The HP-41C is a somewhat legendary reverse-polish notation calculator. The most recent case of that was the PX-41C, a replica of the classic HP-41C. But once in a while, something strikes my fancy and I’ll either raid the junk box or buy the kit. I don’t have a lot of time and I’m usually too busy building my own stuff. I write about a lot of projects for Hackaday, but there are very few I read about and then go actually build a copy of it.
