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Mongrol's MidiboxSEQv4 Build


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#5 - The Enclosure

The enclosure is back from Ponoko with mixed results.

The Good

  • The tab in slot design is so solid that even without screws it holds together beautifully. So much that you can hold it in one hand by the end and wave it about.
  • Black frosted acrylic looks the "dugs baws". It's surprisingly robust too. So far with my fiddling around (see The Bad) there's not a scratch on it.
  • The empty P3 frame with hundreds of little parts makes for a brilliant childrens craft toy. Leave the sticky there and watch them go at it!

The Bad

  • Unfortunately I made a mistake with the front slots. Even with filing, snapping, glueing, more filing, I ended up snapping all 3 of them. Oh well. It's the journey, not the money.
  • Engraving on black frosted doesn't go white and the lettering on this iteration is single line so I can't really fill it in. I'll need to think about this later.

Even though I've snapped it I'm still happy. It's such a big design (some 10 hours work) and Inkscape is too quirky for big time sink designs I'm surprised some slots being missed is all thats wrong.

Oh wait. I haven't put anything in it yet!


Edited by mongrol
Grammar fix
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#6 - Enclosure Bugs & Mounting

I've assessed the enclosure for fitting and worked out the best mounting strategy for all the cards. I now have a definitive bug list for the next cut. I also have a nice wtf moment (or perhaps a senior moment) with my displays.


Bug List

  • Core
    • Audio hole too low. Needs to go up by half. 0.5mm wider
    • USB hole too left. Needs to move right by 2mm and expand 1mm in all directions
  • Display
    • Angle pins need to face right. Face right. RIGHT!!! GEDDIT!
  • Case
    • Sides need to go up by 2mm to give the CS it's 10mm clearance or else buttons will be too high.
    • Fix all slot widths. Sides fit but are a little too tight for comfort an extra 0.1mm would be nice.
  • Top panel
    • Datawheel hole needs to be wider
    • Everything else lines up so great job whomever I stole this panel from (will find out later and credit properly)


To give the CS it's 10mm clearance the sides would need to go either up or the CS down. Unfortunately I have about 2mm clearance to the Core underneath so up they go. This will give a total height of 48mm.

  • PCB's will be mounted on m3 nuts for joint clearance.
  • CS will be 30mm (standoff) + 2mm (pcb) + 10mm spacer.
  • Displays are 35mm standoffs
  • All lower standoffs and nuts need to be tag epoxied to the bottom panel. This is essential to avoid a spinning standoff later and leaving you unable to open the case. You don't want any threaded parts inside a standoff sandwich being able to move.








To keep the nuts to a minimum on the panel meant I had to bottom mount the displays on standoffs. The problem is the IDC socket won't fit between the standoffs so I've put on some angled headers instead (with the desoldering delivering brain damage to one oled). This had proven a very good idea until I realised I had them pointing the wrong way. Both headers foul the CS and display next to them.



More oled brain surgery coming up!

Edited by mongrol
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#7 - CS. The 12mm Alps Encoder Edition

Now I have a fitting panel it's time to solder the rest of my encoders. With the panel in place I can see the first encoder I soldered before is in good alignment so I'm confident in doing the rest of them.

I'm using the Alps 12mm encoder which the CS wasn't designed for. It's nearly half the price of the 16mm part and has a click function for acceleration. Since it's 4mm smaller we need to do some pin bending to get it to fit. Not only that, but some clever people in this thread realised that pins 2 & 3 need to be reversed in order to remove "Detented = 1" (whatever that is, it must be a bad). Still, anything that keeps us soldering and not making music has to be a good thing right? You betcha!

We bend the structural side pins up 90 degrees so they point straight out, then at 90 degrees back down about 2mm out from the encoder body. The 3 encoder pins are bent up to 90 degrees then pins 1 & 3 back down and left at 45 degrees(ish). After some practise, say about 16 times later, you get quite good at this.

P1080828.thumb.JPG.99036b3d9df7eb7f1f82cThe encoders should then fit into the holes quite easily. I used some nose pliers to carefully pop in pins 1 & 3 making sure the encoder sits totally flat on the PCB. 




P1080829.thumb.JPG.0bcc66ae4cbdddd1356eePin 2 is soldered to pad 3 using some left over component tails. Make a U shape of the tail and dangle it over pin 2 with one end into pad 3. It should then be stable enough to solder with 2 hands.



P1080830.thumb.JPG.08f2e7651b415af9a77d4Solder the pad end of the tail and adjust if needed to keep it clear of pin 3 and also away from the LED pads then solder the end on pin 2. Snip off the excess and we're done.

Repeat x16. Rejoice in your new skill then realise there's no more to do.



I then stuck the panel back on and found all 16 encoders in perfect position. A quick connection to the core and displays proved them all working nicely too. At last a post with no drama!

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#8 - LED Fun

Man, this bit was so easy I had my 8 yr old son helping me. I was worried about LED height and Mr Hawkeye advised getting the panel made first so this was the main reason in doing the enclosure earlier than I was expecting. What a great idea! The LED's have a little lip on them so they can't slip all the way through the panel hole, which thanks to (that person who's name I shall get and credit), is a tad smaller than the diameter of the lip.

All I had to do was drop the LED's into the CS. Stick on the panel with it's 10mm standoffs, turn it over and the LED's fell into the holes at exactly the right height. After a quick test I soldered all 40 of them in two go's with none of them going wrong. Win!


Edited by mongrol
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#9 - Fitting and FInished

At last I'm done. I can finally put this beast together. I'm still waiting on a replacement OLED for the one I fried (won't do that again). Just on that I've lots of suppliers punting the same display with different names and descriptions. Check the OLED Displays thread for info. I also still need another run of the enclosure to fix the bugs before I publish the SVG and writeup a build guide for it.

As Captain Barnacle says "Let's do this thing!"


  • P1080837.thumb.JPG.a15b44b3923df4fbe2452Get bottom panel and stick in 12 bolts and nuts for the MIDIIO's and Core. These needs to be 10mm bolts. 8mm no worky.
  • Place the Core and MIDIIO boards.
  • Secure the boards with nuts or little standoffs with the exception of the bottom left core bolt. This needs a 27mm standoff as it rises up to the CS.
  • Make some ribbon cables of a lovely length and route it between the bottom panel holes or else a fouled by standoff you may be.


  • P1080842.thumb.JPG.c0381fd0aa2aab13cd1edThe displays sit on 35mm standoff as they bat right up against the inside of the top panel. In the top right hold stick a little 5mm standoff as it'll have a top panel screw coming downwards (final enclosure will use untapped spacers).
  • Try your best to make a nice neat ribbon cable and fail. Move on with your life.



  • Attach a bunch of 30mm standoffs in the top left corner and along the front. One of two in the middle is nice too. Look! The friendly enclosure designer put holes everywhere in case we need them. What a nice guy.
  • Bottom left standoff on the core is 27mm or 25+ washers. (Bizarrely I got some 27's in a pack of 30's from Jaycar)
  • Stick on the CS REMEMBERING TO ATTACH THE CABLE! (yes I forgot and had to take it apart) and screw on some 10mm standoffs or spacers around the edges and middle. Remember only the edges have top panel holes.
  • Finally clip on the sides, back and top.
  • Shove in a USB and watch the lights come on.
  • Wonder to yourself what is displayed on that dark OLED.



There will now be a short interlude while the final enclosure is finished. Thanks to TK, everyone in the thread for chipping in with advice and that bloke (which will be credited) that I purloined the front panel SVG from.

Mongbox Enclosure thread here.

P.S. I have no idea what this thing does.

Edited by mongrol
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Looking great! If you think the datawheel is sitting a bit high, you can shorten the shaft (encoder shaft or datawheel shaft, depending which one is longer). It is no problem to lower the datawheel by about 5 millimeters using this method.

Many greets and enjoy!



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Question: did you "panel mount" the encoder to the rear of the PCB, bending the legs up to solder (or fly wired)? That's a good way to get the shaft length down. For mine it made the shaft a little too short (so the wheel scraped on the panel) but I spaced it with a bit of plastic in the D mounting hole.

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what we would not do without our moms!
ALPS stec12 have no thread and nut ... not cool for the datawheel
don't think bending and soldering external legs will be solid if rear mouting....
mine is front "panel mount"  ...

EDIT: perhaps soldering the encoder on a piece of perfboard and fixed it with 2 screws/nuts via legs holes on the CS board would do the job....

Edited by tashikoma
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4 hours ago, tashikoma said:

ALPS stec12 have no thread and nut ... not cool for the datawheel

Mine is front mounted. Are you talking about the wheel rubbing against the aluminium collar on the pot not being good? I suppose I could cushion it with a couple of spacers/washers. Widen the hole so it drops down enough, then have it sit on washers instead of down against the bottom of the encoder shaft.

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i was talking about the ALPS encoder . not the wheel rubbing or datawheel knob
in the WILBA design the datawheel encoder is the only soldered on the rear of  the PCB:
with ALPS stec 12 it's difficult to mount it on the rear , bending the lateral fixation legs in a reverse way for soldering is not ideal .
that why on my SEQ i have mounted all encoder on the front of the PCB.

but if you solder the encoder on a little piece of perfboard (with lateral fixation legs straight/centered not externally bended ) and drill holes near each lateral fixation legs on the perfboard (distance between each holes equal distance of the two hole for fixation leg on the PCB)
you could attach/fix the encoder on the rear of PCB with two screw and nuts...so you win some space for the datawheel knob shaft...

sorry for my english , i don't use the good words or syntax.... oops :cencored:

Edited by tashikoma
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It's clear -- you need the threaded bushing in order to panel mount the datawheel encoder, in Wilba's case mounted to the PCB. I forgot you were using STEC encoders. It's no problem with voti or others. In this case Hawkeye's suggesting of filing down the shaft is probably the easiest. With the perfboard idea, I think it might be a bit unstable n'est-ce pas?

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Ok got it. My Alps STEC is front mounted on the PCB and is pretty solid there. I've looked and even if I widened the cutout to let the wheel through I'm not going to gain anything as the flat of the shaft is flush with the top face of the panel. So I'm just going to shorten the datawheel stem. Easiest solution.

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