My home-built computer, crooked boards and all.

Earlier this year, I set out to build my first computer, an RC2014. The RC2014 is a small modular computer. It is available as a kit and is designed to be an entry-level retro home-built computer. Once the computer is assembled, you can program it using Microsoft BASIC or Z80 machine code. I want to share my experiences as a beginner electronics hobbyist, what I learned from assembling the kit, and some of the mistakes I made. If you’ve never considered electronics as a hobby before, I hope this gives you an accessible look at what it’s like.

Headers, dip sockets, jumpers and barrel jacks

The kit is designed to be straightforward, but being a beginner I had to do some Googling. For example, it helps to know what a right angle header is, how to make sure components in the circuit are connected the right way around, and how to tell the difference between a 2k2 resistor and a 3k3 resistor.

The RC2014 backplane has eight slots to connect your printed circuit boards (PCBs). It’s easiest if you can connect the four larger PCBs (CPU, ROM, RAM and Serial I/O) to the middle four slots. However, if you need to connect them to the outer slots, there are just some horizontal links that need to be soldered. I also got the Digital I/O board (an optional extra), which I connected to one of the outer slots.

The tools for the job

Electronics projects like this require access to a few tools, chief among them being a soldering iron, as the RC2014 kit requires over 600 soldering joints. A multimeter is another important tool, which is very useful for testing connectivity between points on the board. If your multimeter has a frequency setting, you can also use it to check your clock pulse. You may find a magnifying glass helpful too, especially if your eyesight is not good.

I was lucky enough to be able to borrow most things I needed. I bought the side-cutters new so I could get a nice sharp pair. I also bought my own roll of solder. If you don’t know anyone who has the tools and you don’t want to buy them, it’s worth checking out whether there is a local makerspace that lends equipment. They may also offer some help and advice.

Magnifying glass, solder, soldering iron, multimeter and mini side cutters.

I did a little soldering and electronics at high school and I really enjoyed it, but that was seventeen years ago. I was very much out of practice, so I wanted to sharpen my skills before putting iron to board. I practised by soldering wires to a few small boards. If you don’t know the first thing about soldering, there are some good tips here and here, and a detailed guide here.

Once I was feeling somewhat happy with my soldering (which took a few days) I started soldering the headers onto the backplane. The backplane is the last board shown in the assembly guide, but if you start by soldering five 40-pin headers onto the backplane, you will have completed 200 soldering joints before moving on to some of the more fiddly components. I thought it was a good way to build confidence.

Highlights

It was very exciting to get a clock pulse out of my clock PCB. I’d never soldered a clock crystal before, and I was very careful with it. It was the last thing to go onto the PCB, and I soldered it quickly, so as not to risk damaging it with too much heat.

The silver component is the clock crystal.

When I connected my clock PCB, powered it up and checked it with the multimeter, it showed 7.37MHz. It’s a 7.3728MHz clock crystal so that is the correct number of megahertz, hooray!

I decided to take a little video on my phone, and the clock pulse actually interfered with the recording. My phone picked up a radio frequency signal generated by the clock, causing a little “pk-pk-pk-pk” sound to be recorded. This was unexpected and really fascinating.

The other big highlight was of course when I finished assembling the computer and connected to it from a serial terminal on my laptop. It took a little bit of fiddling to figure out the permissions and the right serial line, but I was very satisfied to finally see my little computer come to life. My first BASIC program printed the line “Emma is the greatest” ten times.

The Digital I/O board is lots of fun too. The board has eight pushbuttons (digital input) and eight LEDs (digital output). Below is an example program that makes use of the Digital I/O board’s LEDs:

10 FOR F=0 TO 7

20 OUT 0,2^F

30 GOSUB 100

40 NEXT F

50 FOR F=7 TO 0 STEP -1

60 OUT 0,2^F

70 GOSUB 100

80 NEXT F

90 GOTO 10

100 FOR X = 1 TO 150 : NEXT X : RETURN

Cylon scanner program using the digital I/O board.

My mistakes

Most of my mistakes were around components being soldered on a bit crooked or at varying heights (see images below). I tried to get the components to sit where I wanted them using bits of card and electrical tape but this didn’t always work out well. There are apparently various tools to help with component placement, but I think a bit more practice, patience and care would have gone a long way too.

The good news is that it doesn’t stop the computer from working! I found the process was quite forgiving of a few wonky parts.

The heights of the LEDs are really inconsistent.

The header is not quite flush with the board.

I didn’t really plan the layout of my computer in advance, so I ended up soldering on all my right-angle headers facing the same way. I also didn’t really realise it was an option to solder them on the other way. This, in addition to some of them being a little crooked, meant that I had less choice in where I could put each PCB without them leaning against each other.

What’s next?

Next up I need to put my computer in a case that will keep it protected. After that, there are lots of possibilities for upgrading a little computer like this. There are kits to add keyboards and displays, and to run the CP/M operating system. There are also larger backplanes that give you more slots to play with. I think I’d really like to add a sound card and play some music.

If this is the kind of content you like to see, let me know below or on Twitter. And if you just want to talk about any technology projects you’re working on or thinking about, I’d love to hear that too.