For my first attempt at using a PCB (printed circuit board), I have tried to build the ‘Single-Chip Space Invader’ synth from ‘Junkyard Jam Band’, a DIY electronics book written by David Erik Nelson. This is a very simple synthesiser that uses two oscillators to create a sound that should resemble the synths from old video games. It can be either be controlled by a red button that triggers notes individually, or a switch can be flicked to make the synthesiser keep producing a continuous note whilst the user twists the knobs (potentiometers) around to control the pitch.

I have only attempted soldering once before, and that was in my first year at LCC when I made a contact microphone – I found it difficult. I was a little apprehensive to return to it, however I am going to need to learn how to do it for my final circuit, so it’s best to have something else to practice on first! I followed the step-by-step guide in the book, which was very helpful. I started by soldering a switch, LED, resistor and battery clip together, which looked this:

I then soldered some wire to the three potentiometers and the button and switch controls. I then connected the output jack, switches and 10k ohm potentiometer together. After this, it was time to start adding components to the PCB. The first to go on the board was an IC, similar to the one I used on the breadboard circuit a few weeks ago.

One problem with this project is that I have been using a PCB with a different layout to the one shown in the book, which is pretty much the same design as the breadboard I was using a few weeks ago. This PCB only has long vertical connections, and no breaks in between them at all. This meant that in order to avoid a short circuit, I had to scratch away at the metal between the two sides of the the IC with a file so that they weren’t connecting. I ended up being able to do this quite easily, although the layout of the PCB would prove to be more confusing to me later…

I kept going with the synth, soldering jumper wires and capacitors in:

I did have a problem with the capacitor at the bottom, where the legs weren’t long enough to bridge the gap between holes that the book was telling me to make. I solved this by getting a piece of wire and soldering it along from the hole below the capacitor to the hole where the capacitor was supposed to go. As the board is connected vertically, this meant that the wire was still making the same connection as the capacitor was supposed to.

One of the first big mistakes I made was to solder the red diodes in the wrong way around as I didn’t realised they were polarised. When I realised I’d done this, instead of trying to desolder the joint, I just clipped the diodes above the joint and soldered them each one row up. This would work, however I was leaving myself less and less room on the board which was soon going to become a problem.

I kept soldering and eventually added all the switches and potentiometers to the board, which looked like this:

However, my problem came when trying to add power. I started to get confused due to the different layout of my PCB to the one in the book. As the one in the book had a layout with two separate vertically connected lines at the bottom and top, it made sense to me how Nelson was adding power to the circuit as it was pretty much the same concept as what I had done before with my first circuit. However, I was starting to run out of room on my PCB, especially at the bottom, so I really wasn’t sure how to connect it all up to power. I could’ve maybe worked something out at the time, however I was really unsure of my knowledge of circuits and soldering at the time and wasn’t feeling confident enough to change the routing of the circuit. As I was eager to get a start on my final project, I decided to leave this synth for now, however I will be coming back to it (or rebuild it) in the future, as at the time or writing I am now feeling a lot more confident with circuits and I was very nearly finished with it.