Thanks for deciding to give the Motion Meter DIY Kit a go! This could be a thrilling adventure with tiny components to build a fabulously colourful attenuator.
Before we go any further a couple of people have reported their kits are missing a 10pf capacitor. Please check you have 11 (eleven) of the 10pf capacitors – like little discs on legs (scroll down for a photo). If you are missing one please contact Befaco or Thonk and we’ll get one sent out to you. Sorry about that.
Befaco has this amazing thing on its website called an iBOM. It’s an interactive Bill Of Materials that shows you where the components go on the PCBs. It’s awesome and more experienced builders will probably find it’s plenty enough to get you soldering.
But for the less confident builder, I’m going to take you through, step by step, resistor by diode, so that you end up with a marvellously functional Molten Motion Meter. There’s also a build-along video to guide you through the process so you can see how I put the thing together.
This build does involve some surface mount components (SMD), which is very exciting and nothing to be afraid of. There are already some SMDs preinstalled on the Control PCB. This includes the three rings of tiny LEDs. It’s very important that you are mindful of these when soldering or cutting off legs. They are fragile, and the module will break if you mess these about.
Beware the rings of LEDs! Keep cutters and iron away from them!
Find a bit of space on a comfortable desk and place everything within easy reach. All you need is a soldering iron, some solder and a pair of cutters to take the legs off, but there are a few extras I’d recommend.
- Soldering iron with sponge.
- Safety specs.
- Magnifier – we are dealing with small components so some kind of loupe, magnifying glasses or glass would be really helpful.
- Desktop fan – to blow away solder fumes, particularly if using leaded solder.
- Steel wool iron tip cleaner – good for keeping the tip of the iron shiny.
- Helping hands or PCB holder – I don’t use them, but people do like to recommend them to me.
- Ambient electronic music, obviously. This is going to take a few hours, so soothing generative music will help keep you focused and relaxed.
- Tweezers for the SMD.
- Solder sucker – in case things go wrong.
Make yourself a nice cup of tea. Warm up your iron.
What’s in the box?
A Bill Of Materials (BOM) is really useful in making sure you have all the right components and helps you to identify them. Rather than listing everything here, I’ll list the components at the point at which we’re adding them so that you don’t have to keep referring back to earlier in the guide.
In the box you will find:
- Two red PCBs: The “Control” PCB with the rings of LEDs and the “Main” PCB.
- The front panel.
- Bag of resistors, diodes, ferrite beads and the two SMD chips.
- Bag of capacitors, transistors and connectors.
- Bag of front panel hardware, knobs and sockets.
- Bag of ICs and IC holders.
- Bag of knobs, knurlies and the LED lightpipe crowns.
- Eurorack ribbon power cable.
- Befaco’s printed assembly guide.
Ready to go? This is going to be fun, thoughtful and probably a bit fiddly. The general rule is to start with the components that are lowest in height off the PCB and work up to the larger ones. This is so that when you turn over the PCB to solder, the components are held in place by the desktop and don’t drop out. Usually, this means you start with resistors, diodes and then the smaller capacitors, IC holders, large capacitors, and finish off with the hardware. But we have two SMD chips to solder that are lower than anything, so let’s start there.
These are adorably tiny 8-legged chips that come in a black plastic holder. Be careful when getting them out so that you don’t lose them. These do not have legs that go through the PCB; instead, they sit on top, and you solder the legs to pads on the surface. It’s the sort of thing machines should really be doing, but people can do it too, even people like you.
For this, I recommend donning a pair of magnifying specs and using a pair of tweezers. There are different approaches to this, but what I do is put a small blob of solder on one pad and then heat it and use tweezers to push the SMD component into the solder.
So, grab the Control PCB, turn it over and find IC9 and IC10. Pin 1 is labelled, and this corresponds to the line on the IC. Get your iron and add a tiny bit of solder to the pad of IC9 next to the 1. Then take one of the ICs carefully with the tweezers. Make sure it’s the right way around and line it up to the pads.
Heat the pad to melt the solder and slide the IC onto the pad. Make sure it’s central and all the legs are on pads, and while still holding it in place, remove the iron. Give it a moment, and the solder will cool. If it’s wonky, reheat the pad and adjust. Then carefully solder the rest of the legs to the pads. Do the same with IC10. When you’re done, check for bridges between the legs and award yourself an SMD achievement badge.
There are 48 resistors to solder across the two boards. R1 – R25 on the Main PCB and R26 – R48 on the Control PCB. I tend to do them in batches of around ten at a time. Much more, and it becomes thick with legs and more difficult to solder.
|Qty||Value||Code||Name on PCB|
|26||100k||Brown, black, black, orange, brown||R7, R8, R17, R18, R19, R20, R23, R26, R28, R29, R30, R31, R32, R33, R34, R35, R37, R38, R39, R40, R41, R42, R43, R44, R45, R46|
|6||120k||Brown, red, black, orange, brown||R2, R5, R12, R13, R14, R15|
|5||10k||Brown, black, black, red, brown||R3, R11, R16, R22, R25|
|5||1k||Brown, black, black, brown, brown||R1, R6, R36, R47, R48|
|3||30k||Orange, black, black, red, brown||R4, R9, R10|
|2||11k||Brown, brown, black, red, brown||R21, R24|
|1||560R||Green, blue, black, black, brown||R27|
Let’s start with the twenty-six 100k resistors. Put the seven on the Main PCB and solder them. They are labelled in numerical order from top to bottom on the PCB, and R7 is about halfway down. Cut all the legs off with your snippers. Add the rest of the 100k resistors to the back of the Control PCB in batches of about 10.
Beware the rings of LEDs! Keep cutters and iron away from them!
Also, there are a couple of places where resistors have connected pads. Be careful not to block the other hole when soldering or do not solder until both resistors are in place.
Next, solder the six 120k and five 10k resistors to the Main PCB. While 10k should be brown, black, black, red, brown, the red on mine looks very orange. When in doubt, measure them with a multimeter. I did, and they are definitely 10k. And actually, it looks a lot more like red when installed on the red PCB.
Now do the five 1k, three 30k, two 11k and single 560R to complete the resistors. R1 is tricky to see – it’s vertically above R2. Keep a couple of resistor legs handy for the Ferrite beads in the next bit, and this is a great place to go and get a coffee.
Diodes and Ferrite beads
The diodes are the chunky 1N5817 black ones with the silver stripe. These are to do with power regulating and are D1 and D2 on the Main PCB at the top with the overlarge pads. Note the orientation. The silver band on the diode has to match up with the line o the PCB. So with D1 the silver is to the right; on D2 it’s at the top.
The Ferrite beads are two small grey beads that are probably hiding at the bottom of the resistor bag. Use a couple of trimmed resistor legs threaded through the beads to mount them on F1 and F2 on the Main PCB next to the diodes.
You’ll find these in the bag with the ICs pushed into a block of foam packing. We’ll leave the ICs to one side until later on and focus on getting the holders soldered into the Main PCB. The orientation is very important. You’ll see on the PCB that there’s a little nick or semi-circle cut out of one end. You’ll find a similar nick on the IC holders. These should match up to ensure that we put the ICs in the right way around.
You can put them all in at once and then see if you can turn the PCB over without them all falling out. I tend to put a piece of card or plastic over the top, hold it firmly, turn it over and then slide the card out, so it’s flat on the desk. You can also bend the corner legs or use tape or blue-tac – whatever works for you.
Solder one leg of each of the IC holders and then turn the PCB over to check that they are straight. Once satisfied, solder the rest.
In the bag of capacitors, you’ll find nineteen 100nf, eleven 10pf and two 22pf. These are regular non-polarised capacitors, not the big barrel electrolytics which we’ll do later. The 10pf are the disk type and are easy to spot. The 100nf and 22pf ones look exactly the same like mini dipped pacman ghosts. The 100nf have “104” printed on them and in amongst them, you’ll find a pair of the 22pf that have “220” printed on them.
|Qty||Value||Code||Name on PCB|
|19||100nF||104||C3, C4, C5, C9, C10, C13, C14, C17, C18, C19, C20, C23, C25, C26, C60, C62, C63, C66, C67|
|11||10Pf||10||C8, C11, C12, C15, C16, C24, C28, C59, C61, C64, C65|
As with the resistors, do them in batches of around 10. They are spread across both boards, and it doesn’t matter which way round they go. Off you go.
Crystal and Voltage regulators
The Crystal Oscillator is the silver slab and goes in Q1 on the Main PCB.
The voltage regulators look like transistors, and there are two types. The LM4040 are the straight-legged ones and go into REG-1 at the top of the Main PCB and REG-2 at the bottom of the Control PCB. The other two with the wonky legs are the 78L05 and go into IC1 and IC2 at the top of the Main PCB. Orientation is important, and the screen print shows you the flat edge that corresponds to the face of the regulator.
These are the traditional-looking barrel capacitors. These are polarised, which means they have a positive and negative side. The long leg is positive and the stripe on the side indicates the negative. The + and – is printed on the PCB so just stick the long leg in the hole with the + sign. These 4, C1, C2, C6 and C7 all go on the top end of the Main PCB.
Pin Headers and sockets
These are notoriously tricky, and it’s very easy to get these a bit wonky. We’ll start with the headers; that’s the ones with the pins sticking out both ends. These go on the Main PCB at JP1, JP2 and JP3 with the 2×5 on JP1, 2×4 on JP2 and 2×3 on JP3. Place them on the same side as the rest of the components so that the shorted pins go through the PCB. You may have trouble turning them over, so use the same method that you used with the IC holders.
These must be soldered straight as along with the sockets this is what connects the two boards together. So, solder a single pin. While doing so press down on the board so that the header remains straight. Then turn it over, check that they are straight and solder the rest of the pins.
For the sockets, what I like to do is place them on the headers and then place the second PCB over the top. This ensures that they will line up correctly when you come to assemble the module. You can place them directly on the Control PCB in JP4, JP5 and JP6 but make sure you solder them dead straight. Also, putting the boards together now in this way will highlight any components that are getting in the way.
Once soldered, gently pull the PCBs apart again.
The power connector goes on the underside of the Main PCB. You can see by the screen print that the notch faces into the board. To keep it flat when you turn it over, use the foam packing with the ICs in it to prop up the other end.
As you’re soldering on the component side of the board, be wary of leaning the iron against other components and melting them.
Let’s install the ICs in the holders. When you try to place them, you may find that the legs are splayed a little wider than the holder. You can get a cool little tool that sorts them out for you. Otherwise, gently rock one row of legs against your desk and apply pressure until they bend just a little bit.
Orientation is vital here. The larger two Ics have nicks out of one end like the IC holders do. That needs to match up. The smaller ones have a dot in one corner – that dot needs to go towards the nick on the holder. Carefully place them on top of the holder and apply pressure to ease them into the holder. The 8 legged ones are all the same, the larger two fit where they fit.
All the hardware elements come in one bag. These include the knobs, sockets and switches.
Let’s do the switches first. They are all the same and don’t have an orientation.
Place them on SW1, SW2 and SW3 on the LED side of the Control PCB. All the hardware is going on this side. They fit nice and snug; just make sure they are straight as they will have to fit through gaps in the front panel. Solder one leg – check and you can also try dropping the front panel over them to make sure – solder the rest.
Be wary of the header sockets as they are very easy to accidentally melt.
There are 3. They go in the middle of the 3 rings of LEDs. We’re not going to solder them, we’re just going to place them, and then once the sockets are added, we’ll put on the front panel to ensure everything is aligned correctly and then solder them.
The pots push firmly into place. I put the three prongs in first and then wiggle the supporting lugs through the holes. DON’T SOLDER.
The sockets go in two rows of three at the bottom of the Control PCB. The protruding legs face each other and actually go in the same hole between the row pairs. It’s slightly off-centre for the outside pairs. DO NOT SOLDER.
In another bag you’ll find the LED lightpipe crowns. Put the front panel face down on your desk. Place and align the crowns into the ring of holes with the short ends pointing down. STILL NO SOLDERING.
Place the Control PCB face down onto the front panel so the knobs go through the holes, and carefully lift the panel up so not to dislodge the crowns. Wiggle it until the knobs, switches and sockets all poke through. Being careful to hold it together, turn it over so the front panel is facing up.
Now we need to secure the front panel. In the bag you’ll find 9 nuts; 6 black and 3 red. 3 of the black ones are ever so slightly larger – these are for the pots. The other 3 black nuts are for the input jacks, the 3 red ones are for the output jacks. Screw the nuts onto the jack sockets first, and then do the 3 pots.
Make sure everything is flush, and now you can turn it over, balance it on the pots and solder in the knobs and jacks.
Before putting the two PCBs together, we need to add two stand-offs that secure them. It’s a bit fiddly but use your fingers or some tweezers to get the nut between the PCB and front panel and then screw the stand-off into it from the underside of the PCB.
Marry up the two PCBs, bring them together and then screw the two screws into place.
Turn the pots all the way round to the left and place the knobs on top, and line the white pointer to the very left end of the white almost-circle. Push them on nice and hard. They should go all the way flush to the front panel. I find that if I put one knob face down on the edge of a desk, I can apply enough pressure to push them fully on. Do it right, as these are not coming off!
You have completed your Molten Motion Meter, and now all we need to do is plug it in and see if it works.
Plug in the power ribbon cable – it can only go in one way round with the notch towards the module, red stripe to the left as you look at it from the back. And then plug it into your rack.
On power up, you should get a little snake of LEDs going from bottom to top. There should be no smoke. Then if you turn all three knobs fully left, you should get a single LED lit at the top of each ring.
Using the switch, select Audio, and it should be green, purple for CV and orange for inverted CV. Turn the knobs, and you should see a ring of lights all the way around.
Plug in some audio or CV, and the LEDs will respond to the signal, and you can then use the knobs to attenuate. Please refer to the manual for how to use the Molten Motion Meter.
If something’s not working or you’re not getting any lights, please examine your soldering very carefully. The majority of issues come from solder bridging connections or things being in the wrong way around. Re-solder joints that don’t look right and be methodical. The solution will be in your soldering.
That’s it! I hope that was fun and that the Motion Meter is a shining light of usefulness in your rack. Thanks for buying this kit, and in the meantime, go and make some tunes.