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Moraydular Power Bus

A compact (50x200mm) 12-way power distribution PCB for Eurorack modular synthesizers.

Can be built as a simple passive bus board with shrouded or unshrouded headers, using flat connectors / mounting tabs or .156" connectors for power input. Optional power indicator LEDs (highly recommended!) and onboard minimal +5V regulation from +12V rail may be added.

Plain PCB

Populated PCB

Ordering and Building Notes

The file moraydular_powerbus.dip contains the PCB design in DipTrace format. The Gerber files are confirmed to pass checks for Seeedstudio, 5x20cm 2-layer PCB. They will probably work fine as-is for Itead, Tinysine, Elecrow and other prototype PCB services. Consider spending extra for 2+ oz copper traces for improved performance.

Populating the PCB should be relatively straightforward. Some notes:

  • The LED polarity follows standard convention: the short leg / cathode / notched side of LED goes where there's a notch in the silkscreen.
  • The pads for connectors have quite wide thermal reliefs, so soldering them may require some extra heat and patience. In particular, the -12V (bottom row) pins in ribbon connectors will take some warming up for the solder to flow properly.
  • When using mounting tabs, you may want to solder them on both sides for extra sturdiness because it usually takes some force to detach the cables.
  • If not building the +5V adapter, leave out parts as indicated in BOM below

When using onboard +5V in multiple bus board system, either build the regulator circuit for all boards and leave out +5V link cables or populate the regulator circuit for just one board and distribute +5V to all boards. Never link +5V rails of two boards together if they both already have their own +5V feeds.

Bill of Materials

For plain passive board:

  • 12x 16-pin (2x8) 0.1" shrouded box header (eg. Reichelt WSL 16G) OR unshrouded pin strip
  • 6x PCB-mount Faston / Abiko style mounting tabs (eg. Reichelt FS-P 6,35)
    • Alternative: 1x 4-pin 0.156" PCB mount connector (MTA156, Molex KK .156)
    • Or you can just solder the wires from PSU directly to the PCB
  • 3x 3mm LEDs
  • 3x Current limiting resistors according to LEDs you've chosen (2x 1K, 1x 220R as indicated on PCB silkscreen should be fine at least for normal red or green leds)

For +5V onboard regulation add the following:

  • 1x 7805 voltage regulator
    • Use a heatsink according to your planned current draw
    • Pin-compatible DC-DCs such as OKI-78SR-5/1.5-W36-C should work and provide more current with better efficiency and no heatsink required, but currently untested
  • 2x standard rectifier diodes, any of 1N4001...1N4007 will do
  • 1x 10uF electrolytic capacitor, 16V or higher voltage rating
  • 1x 100nF ceramic capacitor

Wide Version

Also included in the repository is a wide 14-way variant (moraydular_powerbus_wide) with roughly 50x380mm size, and .156 connector footprints on both ends. The functionality and design are otherwise essentially the same as with the normal narrow version. The parts list differs only by the two additional box headers / pin strips required.

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