DU-RDT SMD Build Manual

Bill of Materials

1DU-RDT Front Panel
2AlphaSR1712F-01081P8T rotary switch
2Eagle450-4760D-shaft knob
1PanasonicESB-33133DPDT switch
1E-switchTACBLKswitch cap
1E-switchTL1105DF160Q13mm tactile switch
9QingPuPJ301M-123.5mm mono jack
9knurled nut
1NXP74HC7014Dhex buffer (SOIC)
274HC164D8-bit shift register (SOIC)
174HC74Ddual D-type flip flop (SOIC)
174HC86Dquad XOR (SOIC)
5LED, green 3mm
50.320" LED spacer
61N4148small-signal diode (SOD-123)
5MMBT3904NPN transistor (SOT-23)
5220Ω resistor (0603)
101KΩ resistor (0603)
310KΩ resistor (0603)
4100KΩ resistor (0603)
50.1μF capacitor (0603)
12 x 8 0.1" pin header

Our Mouser project cart has most of the necessary components.

Note that the rotary switches stocked at Mouser have a longer shaft than the ones shipped with the kit; this can be fixed with a Dremel, since they will be covered with knobs anyway.

Build Procedure

General Advice

Check that your kit contains all of the parts listed in the BOM above before starting. Pay attention to the resistor values and the orientations of the diodes, LEDs, and ICs. Note that the 78L05 is optional, and should not be populated when using the 16-pin bus header.

Step 1: SMD components

Solder all of the SMD components to their respective placements. The recommended order is decoupling capacitors, resistors, diodes, transistors, then ICs.

PCB IDPart/Value
LR1 - LR5220
OR1 - OR51K
TR1 - TR51K
AR1 - AR310K
IR1 - IR4100K
C1 - C50.1u
T1 - T5MMBT3904
D1 - D61N4148
SR1 - SR274HC164D


Step 2: Eurorack bus header

The 16-pin Eurorack bus header is the only component soldered to the back of the PCB, as indicated by the silkscreen outline. Solder this header first, as shown. Make sure it is flush against the PCB.


Optional: If you do not have a 5V rail on your Eurorack bus, you may use a 10-pin header, soldered to the bottom 5 pairs of pads, and add a 78L05 voltage regulator in TO-92 package (not supplied in the kit) where labeled.

Step 3: Register delay selector switches

Solder the two large 8-position rotary selector switches to their positions at the top-center of the PCB. The curved spring portion should be oriented upward. Solder the side tabs first, then the pins.


Step 4: Pattern lock switch

Solder the 6-pin pushbutton switch to its position directly below the two selector switches. It has a locator peg that should fit the corresponding hole in the PCB to ensure correct orientation. Make sure it is flush against the PCB.


Step 5: Tactile switch

Solder the 13mm tactile switch in the top left corner of the PCB. Its orientation is not important.


Step 6: Input jacks

Solder the four input jacks along the left side of the PCB. Ensure that they are flush against the PCB.


Step 7: LEDs

Insert the LEDs into their spacers and solder to the locations shown. Ensure that the long (positive) lead is oriented toward the bottom of the PCB, i.e. away from the flat side of the silkscreen outline. When soldering, take care to keep the LEDs straight and vertical, and make sure there is snug contact between the PCB surface, spacer, and bottom surface of the LED body.


Step 8: Output jacks

Solder the five output jacks along the right side of the PCB. Ensure that they are flush against the PCB.


Step 9: Front panel

Carefully place the front panel over the switches, jacks, and LEDs. Screw the supplied washer and nut onto each of the two rotary switches and tighten them down. Screw the supplied knurled nuts onto each of the 3.5mm jacks and tighten them down. Add the D-shaft knobs to the rotary switches and press down carefully until they are fully seated. Add the black switch cap to the pushbutton switch and press down until it snaps on fully.


Step 10: Power cable

Tightly crimp the IDC connectors to the ends of the ribbon cable as show in the image, ensuring that the key is facing inward, and that the arrow aligns with the red stripe. Fold the ribbon cable back over the top of the connector, and snap on the strain relief clip.