Just to reiterate others comments. This is such a great looking and professional kit. No problem with the build, relatively quick with clear documentation. Not much more to say, other than I love it!

I purchased this calculator kit because I love vintage RPN HP calcs, and I didn't have any flavour of an HP-41, which was one of the few I didn't really know how to use.

So I was expecting having fun building it and getting some nice toy i could play with and learn about, but I wasn't expecting a really fully usable and fine machine that could compete with my daily use calculator.

And wow !

First, the kit arrived in 3 days from Mexico to France, excellent.

Second, I was truly impressed by the care and quality of the kit package, every little component in its small bag with a label, everything carefully packed.
Complete with the PC communications USB cable.
Then I saw the top-notch quality of the PCB and front and back planes, so good looking.
Then I built it, and this was quite a picnic.
The only thing is that the bolts and little brass stands are very small so take care not to lose one, because there is not a single spare one !

When building it, take care not to solder any part on the wrong side of the PCB, I did for a switch, then I cried, and also take care of cutting every component lead very short, as the space between the PCB and backplane will be very narrow, and you don't want to have short circuits there.

Then it was fully assembled and : WOW !

That's not a toy, that's an extremely good looking, fine, fully usable HP-41CX clone, far better than the original !

The display is excellent, extremely readable and crisp, the keyboard is very fine, responsive, highly usable.
My only regret is that the [Enter] key could not be made double-size - which is understandable - but at least I would have liked it with a specific colour.
(Note that there is one spare keyboard switch and black cap in the kit, so I could have made it black, and still could if I cared to disassemble it a bit.)

Now for the firmware : That's an accurate revival of the HP-41CX, only with a much better display that can display all the stack registers together, have more customization options, a status bar with a clock, a host of menus with internal display (registers, flags...) and USB link so you can backup and restore the calculator's memory to/from the computer.

And the PX-41CX includes a builtin copy of most of the most useful original HP-41 ROM modules : Advantage pack, Maths, Stats, Finance, Zenrom, Circuits, everything is already there, you only need to activate them from the menus, no need to go looking for ROM files on the web !

This is more than excellent, this is truly amazing !

So I end up with a top-notch, good looking, extremely usable HP-41CX clone that beats the original in every aspect.

And well I'm learning to get the best of it and it has immediately become my favorite, daily use, calculator.

Also I had the chance to exchange a few mails with Alex, who is extremely kind, helpflul and responsive, I'm happy to be able to exchange with the author of such a wonderful device and tell him how happy I am !

The only thing is that you will need to be a bit of a geek if you want to be able to customize the firmware and exchange data with your computer, this part is a bit documented here and there, still that's some geeky stuff, so if you are not easy with installing libraries from github and using command-line utilities, you might have a hard time there, but you don't need this to be able to use the machine.

So well, I'm the happiest buyer of a kit from which I didn't expect that much and ends up becoming the best calculator I ever owned.

Thanks Alex for this amazing product.

I absolutely love my little calculator (PX-41c) that I assembled out of the kit that Alex designed. It is the real deal, in any way imaginable, just a lot better, compared to the legendary HP-41c: much longer battery life, more memory, backlit/better display, easier to configure, in-built clock, running much faster ... and a more compact form factor that allows you to carry it anywhere and not being suspected to carry a gun under your shirt, while otherwise being true to the original key assignments. And once you put everything together, and the magic moment comes you turn it on, seeing it working leaves an incredibly satisfying feeling of accomplishment! You built your own calculator, how cool is that???

Alex has been so very helpful all along, I got responses to any of my questions back from him mostly within minutes. His caring and dedication for his customers and quick turnaround is second to none. And he put even bonus add-ons in the package, thank you Alex!

The HP Voyager series of pocket calculators are legendary and almost impossible to acquire for less than a car payment today. Even if you don't understand the draw of these devices, they are still incredibly useful sitting on your desk or traveling in your bag. They are far more convenient and far more capable than whatever calculator app is on your phone.

The kit itself is far beyond any expectations you might have at this price point. The PCB is clean and clearly silkscreened. All the components come in bags labeled with their values and reference IDs. This means someone with some assembly experience could easily build the entire kit without instructions. Even for a beginner, this project is easily solderable. All the components are through-hole and well-spaced. As long as you have a tip able to get in between the small-ish components, you should be just fine.

The (optional) front and back bezels are machined aluminum with both silkscreen and etchings. Assembling the kit on its own is straightforward, if a bit fiddly due to its size. The standalone kit results in a very usable and attractively utilitarian calculator. Adding the 3D printed "bumper" turns it into a commercial-quality device.

The assembly instructions are straightforward but a bit brief. You should read through them entirely before starting to understand the process. There are a few details that you will need to infer through the process of elimination. However, the build is completely reversible at any point, so any mistake should be easily recoverable. A P0 Phillips screwdriver is required, and a micro needlenose plier is strongly recommended.

I ordered this to supplement my growing collection of calculators, and after some initial hiccups, it is working great now and I am considering buying the 41C version with the shorter buttons (since they are interchangeable by uploading different firmware).

The seller was super helpful and responsive to my emails for technical support (I had an apparent issue that was causing it to lockup when you installed the battery). After extensive troubleshooting it turned out to me my soldering job on the crystal - I believe that I had bridged one of the leads of the crystal to the can with solder. Once I resolved this (and fixed another solder bridge that occurred when trying to get the display board re-installed), all worked great!