The Third Man

Midibox 64 - planning questions, your help please??

5 posts in this topic

Hi All,

3 years ago I build a midibox 64, its been great but it was my first project, I am amazed it still works after how badly I soldered it and I didnt secure the PCBS. Anyway I now need to build an upgrade one that is tour ready and reliable and I would love your advise please on some of the details I got wrong

PLAN - itsl be a 64 pot, 48 button plan with 8 strips and an aux area. Each strip will have 1 fader, 5 pots and 4 buttons with additional pots lined up on the right. I havent yet done plot but I know it in my mind. It will not have any LEDS but I may back light it

PREVIOUS MISTAKES - Last time I had panel mounting pots and faders and then made handmade pcbs for the buttons (bad ones) - drawing and etching with a kit. My biggest mistake was I didnt really understand the principle of connects so I hand solder every wire onto the connectors on the AINS and DINS. so stupid. This time I want to use pcbs (i think) instead. the downside is the worry that the pcb doesnt align with my frontpanel. The upside is the stability and reliability of wiring - so here come the questions

QUESTIONS TO ANSWER PLEASE

1, Should I use pcbs to mount the pots - my main issue is wiring all the + and - wires

2, If I do use pcbs should I design one per strip (skipping the faders) and then route all the connects that need to go to ains and dins to pin headers where I can then connect? or shoudl i aim for the top and try and build one mega pcb for the components (i plan to use smash's pcbs for the main parts)

3. I was going to mount the pcbs beneath the frontpanel in parallel - i see bcbox mounted everything perpendicular - is that a better idea - what would you do?

4, if I mount pin headers on my pcbs and use the ones that come with smash boards then I am hoping I can use connectors to easily hook up the two - does this work well and will i need to make up the cables.

Thanks in advance for your help - i know for some these are ridiculous questions but I have searched alot and really need people who know betters opinions. Thanks in advance

Toby

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well.

when im designing a case i start with a 2.54 mm grid, i then get the tech drawings/data sheets for every component im going to use and start from there, this is done on a 1:1 scale so fitment checks are exact.

so i get a sheet of vero or padboard, get my encoders and buttons and place them onto the board, i then take the centre of each component and measure the distance between centres. once i have the measurement between each centre i then use my cad software and enter the hole dimenstions needed into that for the faceplace.

using the padboard i then mount all components and make sure i have space for some 3mm holes to be drilled in the corners of the board and if needed a centre hole for support. with the cad software i would then print a 1:1 scale print of the faceplate and then cut the holes out, take the pcb with parts mounted and test fit, i find printing onto a good stiff paper say a 230gsm is a better option.

with this done i then look at adding headers to the padboard and linking the cables from the components to the headers.

as for mounting, well with the 4 holes , one in each corner of the padboard you can then get your faceplate material, for example say its some aluminium sheet, get some adhesive backed printable paper, print the hole layout for the face onto that at 1:1 scale. make sure your holes etc have got the centrepoints marked.

use a centre punch and put a small puch mark in the centre points of each hole, get a drill bit for the hole, if you can get a slightly larger one thats better, so for instance if the part dimension is 3mm then get a 3.5mm this allows for tolerance. drill the holes.

you would also have the 4 holes for the pcb mounts as well, you can countersink the face panel holes and use csk bolts 3mm this then leaves the heads flush with your face, or if you dont want this then use some dome head 3mm bolts.

so you put the bolts through the front of the faceplate, then on the rear you can fix a 3mm nut and to keep it in place a little dab of threadlock.

should you need a spacer put it over the bolt thread then slide your pcb/padboard onto the back of the faceplate and then use 4 more nuts on the back of the pcb to fix in place.

i will upload some pics later on showing this method to explain it better.

i hope this helps in some way.

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Thanks for this - very helpful.

I ahve two possible plans at the moment. Both involve buying the faceplate in aluminium from schaeffer. This worked so well last time and I dont have the tools or skills to do it anywhere near as pro. However my worry is planning the pcbs designing those and mounting all components on the pcb and then getting that to align exactly with the fronpanel. With due time put in on CAD and the design i should manage this - however

RE PCB BUILD- Should I....

1 - build my own giant pcb to cover all 8 strips excluding faders? PROS - I get one PCB to mount all components reducing the cabling CONS - it would be very big and potentially slower, and the main probblem would be drilling the holes precisely on a large board.

or

2 - design a standard pcb for one strip or maybe two and then buy duplicated from pcb pool? PROS - get exactly what i need CONS - cost and the fact i themn have to mount 8 boards

I am inclined to go with number 2. Whilst this is DIY it needs to have no weak points and Im building it to last. My skills arent great and time is an issue

PCB DESIGN - i need to link the 2 fixed points on each pot together to minimise wiring. I have tried drawing out pcbs and i find if I have more than one strip of 5 pots each next to each other then I need to have a 2 side pcb. Is this right? Do I therefore need 2 sides so the top can deal with the + and - pins and the underside can take all connects to one pin header.

Thanks again

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Anyway I now need to build an upgrade one that is tour ready and reliable and ...

QUESTIONS TO ANSWER PLEASE

1, Should I use pcbs to mount the pots - my main issue is wiring all the + and - wires

As i understand, the more reliable construction is when pots are wired with the wires not on the pcb's. When you need replace damaged components it's easiest way for service works.

Regards,

Janis

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