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Can You Skip the Daughter Boards for Pots?

Started by satriale, December 21, 2020, 03:25:01 AM

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satriale

I'm currently building a Pepper Spray and an IMP v2. However, I'm not a huge fan of the 1590a sizing due to the knob spacing and I'd prefer to put these in some 1590b enclosures. Is it okay to skip the daughter boards for the pots/switch?

I assumed it would be okay if I followed the traces correctly but wanted to double check if there would be any grounding issues or something I'm just unaware of.

madbean

Of course. You just need to know which pads correspond to the appropriate pot lugs. Keep in mind that in some 1590A builds a single wire between the main board and daughter board can cover multiple pots, like for ground or VB connections. So long as you follow the schematic and trace diagram and make the proper connections you can ditch the daughter boards.

satriale

Thank you! I'm only on my 4th pedal so I'm still in early stages of my knowledge.

Looking at the traces/schematics can I assume the empty pads (3rd from left on pepper spray, last on right for imp v2) are ground? That, on the Pepper Spray, the 3rd pad from the left should connect to pins 1 for both harm and balance pots and the middle lug on the switch? If so, someone at my skill level might have some difficulty fitting 3 connections and unless someone has a smart technique I'm thinking of just using the daughter boards. Maybe connect 3 wires to one and shrink wrap?

Thanks again.

satriale

I finished the pepper spray without the daughter board (bat41s sound awesome btw), but I'm getting some loud buzzing when I touch the pots. I think this is a grounding issue but I soldered pin 1 for both pots to the bottom of themselves. Is this not possible with these 9mm pots? For reference, the harm pot's buzz (blue wired) when touched is much louder than the balance pot.

Stomptown

I'm guessing the back of those pots are not in contact with the enclosure like a typical 16mm pot. Do you have a multimeter with continuity setting? If so, I'd tighten one of those pots down and check for continuity between the enclosure and the back of the pot.

satriale

Thank you, I didn't realize that the 16mm pots with the lug wired to the pot case were also grounded to the enclosure like that. I don't have an enclosure drilled for the pepper spray yet but I imagine you're right. I think bringing the ground pin up to the top of the pot would create a connection with the enclosure.

I ended up doing a sort of floating star ground and covering it in heat shrink. With the star grounding, the buzz is a lot lower. Can't wait to box it up!

Given the Imp's complexity, I'll probably just use the daughter board and wire the tone/vol off of the daughter board.

Cheers

Stomptown

#6
I just checked for continuity between the front and back of one those 9mm pots and it turns out they are connected so you can leave things as is.  The noise should go away once it's boxed and those lugs are tied to ground via the enclosure.

Edit: never mind! looks like you ran wires to tie them into ground.  Probably a more reliable solution IMO.

satriale

Yeah I figured it was better since it was designed to be grounded to the pcb, less separate ground points. And since I don't understand what ground loops really are yet...

Good to know these pots have continuity from the bottom though! I was just drilling the enclosure and the drill battery died. At least the buzzing when touching the pots is much more minimal now.