Eurorack Switched-Mode Power Supply (SMPS) – V1.2

The Eurorack SMPS is a powerful power supply for Eurorack Systems.

This is the updated documentation for version 1.2


A very simple and safe solution

Power supplies usually involve a transformer, which implies to deal with Mains voltages.
Mains voltages are extremely dangerous.

The Eurorack SMPS is powered by a plain laptop-style power brick.

Eurorack SMPS Top side PCB
Bottom side PCB
Dimensions

If you’re looking for a linear -low power- solution, then check the Mini Dual Power Supply.

Build instructions

The build process is pretty straight forward. The two DC-DC converters hosts the complex circuitry.

I recommend to start by soldering the two converters.
Then solder the two resistors and the three diodes. Attention, the diodes are polarized. Align the white band on the diodes to the white markings on the PCB.

Attention, D1 is not a regular Silicon Diode. It’s a TVS (Transient-Voltage-Suppression) diode (P6KE 39A). See Datasheet.

Then solder the 2 output terminal connectors, the fuse socket and the DC input jack socket.
If you want you can also use a screw terminal for S1. If so, you can solder it now.

Bolt the 4 standoffs to the PCB.

The two LEDs are also polarized. The longer leg is the positive side. With the front panel, I recommend to measure the distance required for the LED to be correctly placed through the panel, then bend the legs accordingly.
The distance from the PCB is important too. The center of the LEDs is at the same elevation as the center of the brackets’ hole.
A bit longer than necessary is better than too short.

One of the last steps is to bolt the front panel in place, then cut two short length of wire, tin the tips, and solder them to the switch. Then, connect the wires to the screw terminal S1, through the switch’s cutout in the front panel.
Snap in place the switch.
Place the fuse (T2A) in its socket (or in the cover of the socket).

Finished PSU

Tests

Before pluging in anything, triple check your build, and specifically the polarities of the diodes.

Do not connect immediately the new PSU to your system bus! Check first if everything is safe!

Connect a PSU Brick (24V is one of the most common value) to the DC input socket K1 and toggle the switch. The LEDs should lit immediately.

With a multimeter, check the presence of the voltages on K2 and K3: The black (negative) probe of your multimeter is in contact with the middle pin (“GND”) and with the red (positive) probe, measure the voltages at the two other pins on K2 and K3. You must read -12V and +12V.

Documentation

3 thoughts on “Eurorack Switched-Mode Power Supply (SMPS) – V1.2

  1. Hi David,

    I was wondering wat certain abbreviations of some of the components mean.
    RES-AD-10.16-W0.8-L6.6-D2
    DO-15-P10.16
    DO-15-P12.7

    It’s obvious that RES stands for resistor and DO for diode. I would really appreciate it if you could clarify the remainder? Thanks in advance.
    Kind regards,
    Thomas

    1. Hello Thomas!
      The names of the footprints are loosely based on the “IPC-7251 Naming Convention for Through-Hole Land Patterns” document, or on JEDEC or other usual/older package names:

      • “RES-AD-10.16-W0.8-L6.6-D2” stands for RESistor, Axial, Diameter (it’s round), <pin pitch>, W <lead width>, L <body length>, and D <diameter>
      • “DO-15” is the JEDEC code for a diode (see https://en.wikipedia.org/wiki/DO-204), and P10.16 is <pin pitch> of 10.16mm.

      Numerical values are in mm.

      • “LED-3MM” is a 3mm diamater LED
      • “CONV_SKA15x-x is CONVerter and “SKA15” is the MeanWell reference
      • “FUSE-22.6-5×20-PTF78” is of course a fuse, 22.6 is the pin pitch, 5×20 is the size of the fuse and PTF78 is a reference of a fuse holder from Stelvio Kontek
      • “LUMBERG-NEB-21-R” is simply the manufacturer name and the component reference.
      • “SCREW-TERM-5.08-2 or 3” is a Screw Terminal connector, with a pin pitch of 5.08mm and 2 or 3 connections.

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