Your First DIY Module Build

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You can solder, you have a case and power, and now you want to build your first module. This page walks you through a typical DIY Eurorack kit from the bag of parts to the first sound: what to check first, the order to solder in, the checks before power-on and what to do when it doesn't work straight away.

New to soldering? Start with How to Solder. Not sure what a part does? See Electronic Components Explained. Words you don't know? Look them up in the Modular Glossary.

Hand tools starter set
Our hand tools starter set: flush cutter, long nose pliers and tweezers

What you need

Choosing your first kit: start with something simple and fully through-hole, like a passive multiple, an attenuator, a mixer or a VCA. Fewer parts means fewer places for mistakes, and you'll learn the whole process. Save the big digital modules for kit number two or three.

1. Before you pick up the iron

  1. Read the build guide of your kit from start to finish. Many kits have options (jumpers, part values, a 10- or 16-pin header) that you need to decide on before you start.
  2. Check the parts against the BOM. Count everything and tick it off. See BOM: The Bill of Materials for how to read one. Missing parts are much easier to sort out now than halfway through.
  3. Sort the parts by value, for example in a muffin tin or on a strip of tape with the values written next to them. Resistors look alike: read the colour code and measure any you're unsure of.
  4. Check the PCB for which side the parts go on. On Eurorack modules the jacks, pots and switches usually go on the front side (facing the panel) and everything else on the back, but not always.
  5. SMD parts? Many kits come with the tiny SMD parts already soldered on. If yours doesn't, read our SMD sizes guide first and do those parts before anything else.

2. Solder from low to tall

Build order: lowest parts first1 Resistors& diodes2 ICsockets3 Smallcaps4 Transistors& regulators5 Electrolyticcaps6 Powerheader7 Jacks, pots& switchesthe board stays flat on the table while you work
Solder the lowest parts first, so the board lies flat and each part is pressed against the PCB while you solder it. Illustration: Melodio.
  1. Resistors and diodes. Bend the legs, push the part flat onto the board and bend the legs out slightly on the back so it can't fall out. Mind the band on diodes: it must match the line on the PCB print.
  2. IC sockets. Always use IC sockets (8-pin, 14-pin, 16-pin): you can swap a chip later without desoldering. Line up the notch with the notch on the PCB. Solder two opposite corners first, check the socket is flat, then do the rest.
  3. Small capacitors (ceramic and film). These have no polarity.
  4. Transistors and voltage regulators. Match the flat side with the outline on the PCB. Don't push them all the way down; leave a few millimetres of leg.
  5. Electrolytic capacitors. Polarised: the stripe is the negative leg. Check twice, a reversed electrolytic can pop.
  6. The power header. A 10-pin or 16-pin box header with the notch as shown on the PCB. Check where −12V (the stripe) goes.
  7. Jacks, pots, switches and LEDs come last, with the front panel fitted (see the next step).

After every part: check that each joint is shiny and cone-shaped, then trim the legs with the flush cutter. See How to Solder for what a good joint looks like.

WQP518MA jack sockets
WQP518MA jacks, the DIY Eurorack standard

3. Panel parts: fit first, solder second

Jacks, pots, switches and LEDs have to line up perfectly with the holes in the front panel. The trick is to let the panel do the aligning:

  1. Place all jacks, pots and switches in the PCB without soldering.
  2. Put the panel on top and tighten all nuts by hand (a Mono Jack Set gives you a nut for every jack).
  3. LEDs: push them through the PCB and into the panel holes so the front sits flush, then solder one leg. Mind the long leg (+).
  4. Turn the sandwich over and solder everything. Then loosen the nuts, check that nothing is under strain, and tighten them again.
  5. Fit the knobs last. Check whether your pots have a T18 or D-shaft.

4. Check before you power up

A few minutes of checking can save a module, or your power supply.

  • Look at every joint with a magnifier or your phone camera zoomed in. Look for bridges between pins, joints that aren't shiny and pins you forgot. Remove extra solder with solder wick.
  • Check polarity of diodes, electrolytic capacitors, the power header and IC sockets once more.
  • Measure for shorts with the chips not yet in their sockets: set your multimeter to continuity and measure between +12V and GND, and between −12V and GND, on the power header. It may beep briefly while capacitors charge, but it must not keep beeping. See Using a Multimeter.
  • Clean the board with isopropyl alcohol if your solder left a lot of sticky flux.

The ribbon cable is the number one cause of dead modules. The red stripe (−12V) must match the stripe or −12V mark on both the module and the bus board. See Make Your Own Eurorack Power Cables.

5. The first power-on

  1. Insert the chips with pin 1 (the notch or dot) matching the notch on the socket. Straighten the legs first by pressing the side of the chip gently against the table.
  2. Connect only this module to the bus board, with the case switched off.
  3. Switch on and watch for a few seconds. Any smoke, smell or crackle: switch off immediately. Then carefully touch the chips and regulators: nothing should get hot.
  4. Test the function with a simple patch: an oscillator into the input, the output to your mixer or headphones. Our Patching Techniques page has ideas.
  5. Calibrate if the build guide says so. Oscillators usually need tuning with the trimmers (1V/octave and offset) after warming up for 15 minutes.
  6. Digital module? The microcontroller may need firmware first. See Flashing Firmware: STM32 and AVR.

It doesn't work: what now?

Symptom Likely cause What to do
Nothing at all, no LEDs Ribbon cable reversed or loose, power header the wrong way round Check the stripe at both ends. Measure ±12V on the module's power header.
A chip or regulator gets hot Chip in the wrong way round, a short, a reversed part Switch off at once. Check chip orientation and look for bridges near that chip.
Works partly, one output or knob does nothing Forgotten or cold joint, wrong resistor value Reflow the joints in that part of the circuit. Compare resistor values with the BOM.
Very quiet or distorted Wrong resistor (gain), wrong op-amp, missing capacitor Measure the resistors around the op-amp. Check the voltages on the IC pins against the schematic.
Oscillator out of tune or doesn't track Not calibrated yet, or cold/unmatched transistors Let it warm up and follow the calibration steps. See the repair guides.

For a deeper approach to fault-finding, see our Repair Guides. And don't be shy: most kit makers have a forum or Discord where builders help each other.

FAQ

How long does a first build take?

A simple utility module takes an evening, a VCO or filter with 100+ parts a weekend. Take your time: rushing is how mistakes happen.

Do I really need IC sockets?

They're not required, but they make repairs and swaps much easier, and they protect the chip from heat while you solder. For a first build we always recommend them.

Leaded or lead-free solder?

Leaded solder (60/40 or 63/37) melts at a lower temperature and flows more easily, so it's easier for beginners. Lead-free is better for the environment but needs a hotter iron. Whichever you use, work in a ventilated space and wash your hands afterwards.

I made a mistake, can I remove a part?

Yes. Use solder wick or a desoldering pump to remove the solder, then pull the part out with pliers while heating. Cutting the part's legs first and removing them one by one is the gentlest way for the PCB.

Where to go next

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