Maddie Hardware · Power
m-power bus
A 20-slot Eurorack busboard for hand soldering. Each module plugs in with a 5-pin JST PH cable, and every rail on every slot has its own fuse.
- Size
- 389.5 × 54 mm
- Layers
- 4
- Slots
- 20 × JST PH 5-pin
- Rails
- +12V · −12V · +5V
- Input
- Mini-Fit Jr 2×3 (×2)
- Parts cost
- ≈ $6.90 per board
Overview
This is the second version of my single-row busboard. Version 1 used SMD parts and 16-pin Eurorack headers. Version 2 has larger pads, so you can solder every part by hand. Each slot has one 5-pin JST PH header in place of the 16-pin header. A JST power adapter connects the cable to the 16-pin header of a module.
There is no CV or gate bus. The 5-pin header carries power only.
Power input
Power comes in through one of two Mini-Fit Jr 2×3 connectors, J21 on the top edge or J22 on the bottom edge. They are wired in parallel. Use only one of them.
| Row | Left | Middle | Right |
|---|---|---|---|
| Top | +12V | GND | +5V |
| Bottom | GND | −12V | GND |
This is the view into the mating face, with the board below. The m-power PSU uses the same pin map, so connect cable pin n to pin n.
Slot pinout
| Pin | Rail |
|---|---|
| 1 | −12V (square pad) |
| 2 | GND |
| 3 | +12V |
| 4 | GND |
| 5 | +5V |
Protection
- Each rail of each slot has a 1.1 A PTC fuse.
- The inputs have fuses and clamp diodes.
- A P-channel MOSFET blocks a reversed +5V input.
- An LED on each rail shows that the rail is live.
Build notes
- All caps and resistors are 1206 and all PTCs are 1812, with hand-solder pads.
- Use PTCs rated for 24 V or more. If a module shorts +12V to −12V, one PTC can see about 24 V.
- The board has four M3 mounting holes, 3.5 mm in from each corner.
- The back has a silkscreen pattern.
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