This kit went together well by following the directions. It takes some care, and a magnifying glass, but it worked right away. I've been having a lot of fun with it and created an interactive adaptation with LEDs under the cores that show the state of the cores. This makes it possible to "draw directly in memory" with a magnetic stylus. Just so you know, shipping can be quite slow to the US, and that's why I rated that 3 stars. Jussi was responsive and the product came through, but it took much longer than either of us anticipated. Overall, I'm very happy with the kit and appreciate the work Jussi put into it!
Here's a link to my interactive version of it: https://hackaday.io/project/163976-interactive-core-memory-shield-using-led-matrix

This DIY core-kit is great. The circuit is well designed and all the components are well to arranged on the print. The whole shield looks very nice. After soldering and loading the Arduino sketch the program works fine. I can read and write to the core's. This shield is a very nice Retro-electronic's learning tool for me.

The kit and the documentation is excellent. Quality is very good, also good quality power connector and the PCB. The kit is quite easy to assembly and gives a lot of fun and ability to experiment with retro-technology. Also contact with the seller is very good.

I totally recommend buying it!

This kit was enjoyable to build, and threading cores was easier than I thought it would be. Took three and a half hours to finish. Only trouble I had was enamel coating on wire was troublesome to solder. It is fun to wave a magnet over memory. I would suggest running "t" test to ensure all bits are writing/reading properly.

I made a video about this kit. It is a fun kit, and very unique.
The arduino program gives you the tools needed to experiment with data storage. All you need is soldering tools, a flush cutter, fine pair of tweesers (I used plastic tweeser, or atleast non magnetized is a must), and an inexpensive Arduino UNO.

The kits needs updated documentation. Resistor values does not match the ones in the schematics, and the images are of the old board. It cause a bit of worry when you are completely new to the circuit. It didn't stop me from succeding in building it though. Also the docs doesn't mention that the 3.3V supply is disconnected from the arduino. It's in the schematics, but it is also a bit unclear what is connected and not (nets +3.3V and 3V3 are not connected ). I hooked the 3.3V up to the arduino's 3.3V and it works fine with the Arduino UNO. "thou shall check voltages" proved itself once again :D

Anyway., great little kit unique of its kind. Here is my video:
https://www.youtube.com/watch?v=rx4fN8Qo9gc

So, I love this little kit. It's a great demonstrator for computer memory to kids in part because they can see the actual bits.

The documentation overall is great. I plan to use this as a demonstrator for teaching about computer memory. I think the tangibility of the cores make it easier to connect some of the concepts regarding a bit. I'm looking forward to seeing if we can flip bits using a small magnet.

The assembly instructions are sparse and there's a few pitfalls.

Assembly will require a good pair of tweezers and a magnifier. I recommend getting some strong reading glasses to ease the process.

Some pointers:
1) Pay careful attention to the wiring map of the memory array and the orientation of the cores. Orient the cores exactly as laid out in the wiring map.

2) C2 & C4 don't exist and are not included.

3) The parts manifest designates the difference between the two transistor types and their placement on the board. Fortunately one is even numbered transistors and the other is odd numbered so once you figure out which is which placement is easy.

4) When soldering components start with the surface-mount capacitors & resistors that mount on the back of the board.

5) When soldering transistors apply all of the odd numbered transistors, solder & clip them. Then all of the even numbered transistors. It gets a little hectic on the back of the board with all 48 leads sticking out and you can't really reach the contacts to solder them.

6) Use a few cm of the 32 ga wire to create a little tool. Loop it around itself and twist off in a spoon shape so you can grip it between your thumb and forefinger. This will make picking up 8 of the little cores simple(er) and you can then transfer them to one of the vertical wires easily.

7) The kit contains ample 32 ga wire. The cores thread much more easily on wire before the enamel is removed. When working with the horizontal wires leave a few couple cm of wire to work with on either end. After threading the horizontal wire use the soldering iron to burn the enamel. Cleaning the carbon off the wire is much easier than sanding the enamel.

8) Check as you go. As you solder each wire in place check the ends for continuity. The enameled wire can get trapped in the solder without making a connection.

9) Use the tweezers to pull the horizontal and vertical wires taut before soldering. This will line the cores up neatly which will greatly ease threading of the sensing wire.

10) The LED (D1) is unlabelled on the board for polarity. + is opposite from the arduino header.

Good luck!

Oh, one more really important thing. THANK YOU for both designing this and making the kit available. That's really a fantastic gift to the rest of us that you've put this out there.

What should I say - a fully working ferrite core memory for Arduino... if you are bored of 64GByte USB-Sticks and multi TByte HDDs, this retro shield is the right thing for you. All parts you need for the smallest USB-Stick available are included in the package and it's a lot of fun to solder your own working core memory... I'm totally satisfied.

By the way, I tried to copy a MP3 to the core memory but failed at writing the file name... 32 bit (4 Byte) is a little bit tight... just kidding...