A brand-new MSX computer in 2022 – Part 2

PCB and components arrived. So many packages, from US, Spain, Czech Republic and China. I bought two sets of PCBs, and they are slightly different. Checking the components and comparing with the PCB footprints I figured out the DIN8 connectors will not fit and need to order new ones. The rest seems to be OK.

The only package that actually costed me a lot of taxes was the one sent by Mouser Electronics. That is because they only use Fedex to send their packages and there is no way around import taxes when using Fedex, the delivery guy comes with a portable credit card machine to charge you 110% of taxes before handle you the package.

<sarcasm>Thanks DRF, love you!</sarcasm>. Anyways, we can start building the MSX now.

I’ll start building the Keyboard, and in this post I’ll document every component I had to buy for the whole build. If you are interested in building a MSX computer or just need a reference for a specific component, you can use the lists I’m documenting here.

Building The Keyboard

For the keyboard I will start building the leveling elements, connecting them to the board and then soldering all resistors, diodes, capacitors, sockets, connectors, and key switches. Then we will fit the key caps appropriately.

First step is to setup the leveling kit that is used with the big keys on the keyboard as well as with the space key. First thing I need to say is that it is not a super easy thing. Those kits are formed by small plastic pieces that need to be mounted in a specific order and side, then the metal bars need to slide into those in the right way, so you get the expected leveling without breaking the plastic.

There is a way to connect the keys to the keyboard that you don’t need force anything. If you are forcing the connection, you are doing the wrong way and the plastic may break.

Keep in mind that you need to slide the small piece of plastic into the big one in a way that you keep the side with the two holes pointing to the place where you will hold the bar. The metal bar slides into the lowest hole.

A good video to understand how to build the stabilizer is available below. I just ignored the tip to cut parts of the pieces. My kit worked very well without any of those recommended changes.

When setting up the stabilizers into the board, connect the big part to the larger hole and gently push the other side of the plastic piece against the smaller hole. You will hear a click and the stabilizer will be mounted to the board.

After setting up the stabilizers and mount those into the board, we can move forward and start soldering the three through-hole 470 ohm resistors to the keyboard. Those are specific as R1, R2 and R3 and have no polarity.

The resistor array (RN1) is a 6 pin 4.7K ohm component that also goes into the board. Go ahead and solder it. As a tip use a piece of tape to hold it and turn the board, solder the first and the last pin, turn over remove the tape, make sure everything is aligned and then solder the rest of the pins.

There are three capacitors to be soldered. Two 0.1 uF, MLCC (C1 and C2) and one 10uF MLCC (C3). Those are not polarized and are located on the superior part of the board.

You will need to solder a 16dip300 socket and a 14dip300 socket to the board. They are also located on the superior part and will hold the logic chips used by the keyboard. The same strategy I explained for the resistor array can be used here. Just use a piece of tape to hold the sockets in place, turn the board and solder the first and the last pin.

Then remove the tape, adjust the socket to the right position (you may need to de-solder a pin) and solder the rest.

The picture below shows the keyboard so far.

Use the same strategy used for the sockets to solder the connector as well. It is a 2×8 pin header, right angle shrouded connector with 2.54mm pitch. It will be used to connect the keyboard to the mainboard using a flat table.

LEDs have polarity and need to be soldered in the right way. Usually, boards are marked with a squared sign where you need to solder the cathode (negative) but the thing is that some boards I soldered before were just the inverse. Apparently, there is no real standard and I usually use my multimeter to detect where is the cathode, putting a probe on the ground and checking the place where the led needs to be soldered. I could only do that to the LED indicated as D1 on the board.

I believe the other LEDs are only activated when you have power on the board and are used to indicate status of specific keys as they are located just under two of them. I’ll come back later and solder those when the boards are connected.

For the space key I bought a better switch from Mouser and that one was super easy to solder. It has small plastic connectors that fit perfectly to the board and leave just the connectors to solder. But the rest of the keys I purchased from AliExpress, and they don’t have those connectors.

They are just fixed by the contacts, and it is a problem to keep them aligned when soldering. The strategy I used was to go four by four using a tape to hold them in position, then turning the board and soldering just one pin. Then I used the solder iron and my hand to kind of align then before soldering the other pin.

It was just a lot of work to get everything aligned but the result was good.

I also didn’t like the fact that my AliExpress source provided different tons of brown for the switches. I believe they are all from the same quality (not super good), and after placing the keycaps nobody is going to notice, but it is annoying to see different tonalities when it is supposed to be just one.

Here is a picture of the almost finished keyboard and a time lapse of the whole process.

Bill of Materials (Reference)

To help others that may be interested on the project I’m pasting Sergey’s BoM here with the links I used to buy the components. Most of them are available from Mouser, UTSource and/or AliExpress. For the main board, I decided to use the Mouser automatic project cart shared by Sergey on his website here, but I’m also including links to the same components on AliExpress if you prefer to deal with them.

Keyboard components I purchased from AliExpress following the links I’m providing below.

Keyboard

Main Board