Building the Gates and Trigger

SCHEMATIC:

PCB:

BOM:

Qty
Value
Device
Package
Parts
Description
2M7DIODE POWERDO214AC 1N4007 equivalent
2LEDLED3MMLED1, LED4LED
3Tact SwitchPTH 6x6x13S4, S5, S6Momentary Switch
1100kRESISTORR0805
4100nCAPACITORC0603C3, C5Non-Polarized capacitor.
2100nCAPACITORC0805C9, C10Non-Polarized capacitor.
1210kRESISTORR0805
113kRESISTORR0805
61kRESISTORR0805
11nCAPACITORC0805C2Non-Polarized capacitor.
61uCAPACITORC0805C1, C6, C7, C18Non-Polarized capacitor.
1270kRESISTORR0805
12k2RESISTORR0805
43904MMBT 3904 TransistorMMBT3904LT1G_SOT23Q2, Q3, Q4, Q6http://octopart.com/mmbt3904lt1g-on+semiconductor-3280
14148DIODE SIGNALSOD80CD1
1430kRESISTORR0805
14k7RESISTORR0805
15k6RESISTORR0805
15z1DIODE ZENERSOD123D2
3 3.5MM SOCKETTHONKICONN-MOD 3.5mm socket for Eurorack modular synths
1OPAMPIC-TL072SMTSO08IC2OP AMP
1Male Header – 4 pin

 

Assembly:

  1. There are two PCBs: A small power PCB, and the main PCB.
  2. Clean the PCBs with Isopropyl Alcohol.
  3. Assemble the small power PCB first:
    1. Install the M7 diodes, two 1u capacitors, and two 100n capacitors. Do not install the left-most capacitors or regulator.
    2. Install the Tile Tail. See picture below for the orientation.
    3. Do not install the 4-pin Male headers. It gets installed on the main PCB later.
  4. On the Main PCB: solder the surface-mount components to the PCB.
    1. Make sure the diode polarity is correct.
    2. The two small unlabelled footprints (0603 size) are 100n bypass capacitors.
    3. Pin 1 for the TL072 IC is by the large white dot.
  5. If using hot-air or an oven to solder the surface-mount components then do this now.
  6. Inspect all of the soldered components for solder bridges between pins and components, especially around the opamps.
  7. Solder the 4-bin male header to the main PCB.
  8. Solder the buttons, leds, and jacks to the front of the PCB.
  9. Attach the front panel.
  10. DO NOT ATTACH THE POWER PCB YET. It will be difficult to fix problems if it is permanently attached now. Solder it into place after testing.

Testing

  1. Inspect PCB for solder bridges between components, loose solder balls, tombstones, etc.
  2. Before powering the module for the first time ensure there are no power shorts. Check that there is no continuity between the pins on the power cable, and across the opamp bypass capacitors (unlabelled 0603 components). Check both PCBs.
  3. Apply power to the power PCB and check that +12 and -12 are on the right pins (labelled on the PCB).
  4. Place the power PCB on the headers without soldering (see picture above for orientation). It may need to be twisted slightly to make contact with all power pins.
  5. Turn power on and test each button. The first should toggle on/off. The second should give a ~10ms pulse. And the third should be on while it is pressed (Momentary). Voltage levels should be between 5V and 6V.
  6. If everything is correct, solder the power PCB into place. Make sure the power PCB isn’t touching any pins underneath.