Assembly instructions

Overview

• 12 V → 5 V regulator
• 6N138 MIDI IN
• 74HC14 fan‑out
• 5 V power‑on LED
• THRU/OUT activity LED
• Pin‑header MIDI jacks
• Full wire‑color guidance
• No grid coordinates

This version is ideal for perfboard assembly where you place parts by eye and follow the wiring map.

🎛️ Wire Color Key

• Red → +12 V input
• Orange → +5 V regulated
• Black → Ground
• Yellow → MIDI signal lines (raw + clean)
• Blue → Logic connections (inverter inputs/outputs)
• Green → LED wiring
• White → Misc short links / regulator wiring

🧱 FULL ASSEMBLY INSTRUCTIONS

1. Build the 12 V → 5 V Regulator Block

78L05 orientation

Flat face toward you:
Pin 1 = IN, Pin 2 = GND, Pin 3 = OUT

Wiring

• Red wire: 12 V input → 1N4007 diode → 78L05 pin 1
  • Stripe on diode faces the regulator
• Black wire: 12 V ground → perfboard ground bus
• Orange wire: 78L05 pin 3 → +5 V bus
• Black wire: 78L05 pin 2 → ground bus

Capacitors

• 100 µF electrolytic: + to pin 1, – to ground
• 10 µF electrolytic: + to pin 3, – to ground
• 100 nF ceramic: between pin 3 and ground

2. Add the 5 V Power‑On LED

• Green wire: +5 V bus → 1 kΩ resistor → LED anode
• LED cathode → Black wire → ground bus

This LED lights whenever the regulator is producing 5 V.

3. Place and Power the 6N138 Optocoupler

Power

• Orange wire: pin 8 → +5 V
• Black wire: pin 5 → ground

Pull‑up

• 10 kΩ resistor: pin 6 → +5 V

MIDI IN protection diode 1N4007

• Between pin 2 and pin 3
• Stripe toward pin 2

4. Install the MIDI IN Header (3‑pin)

Header pin mapping:

• Pin 1 = DIN pin 4
• Pin 2 = DIN pin 5
• Pin 3 = DIN pin 2 (GND)

Wiring

• Yellow wire: header pin 1 → 220 Ω resistor → 6N138 pin 2
• Yellow wire: header pin 2 → 6N138 pin 3
• Black wire: header pin 3 → ground bus

5. Connect 6N138 Output to 74HC14 Input + MatrixPortal RX

6N138 output

• Pin 6 = raw MIDI logic output

Wiring

• Yellow wire: 6N138 pin 6 → 74HC14 pin 1 (first inverter input)
• Blue wire: 74HC14 pin 2 (first inverter output) → MatrixPortal RX

Important

74HC14 pin 2 is the “clean MIDI” signal.
All THRU inputs will come from this pin.

6. Place and Power the 74HC14

Power

• Orange wire: pin 14 → +5 V
• Black wire: pin 7 → ground

7. Fan Out the Clean MIDI Signal to All THRU Inputs

All THRU inverters must receive the same input from pin 2.

Wiring (all blue)

• Pin 2 → pin 3
• Pin 2 → pin 5
• Pin 2 → pin 9
• Pin 2 → pin 11

This feeds the clean MIDI signal to all four THRU channels.

8. Add the THRU/OUT Activity LED

This LED shows the buffered MIDI signal.

Wiring

• Green wire: 74HC14 pin 2 → 1 kΩ resistor → LED anode
• LED cathode → Black wire → ground

9. Install the Four THRU Headers (3‑pin each)

Each header uses the same mapping:

• Pin 1 = DIN pin 4 (from +5 V via 220 Ω)
• Pin 2 = DIN pin 5 (from inverter output via 220 Ω)
• Pin 3 = DIN pin 2 (GND)

10. Wire the THRU Outputs

THRU1 (inverter B)

• Blue wire: pin 4 → 220 Ω → header pin 2
• Orange wire: +5 V → 220 Ω → header pin 1
• Black wire: header pin 3 → ground

THRU2 (inverter C)

• Blue wire: pin 6 → 220 Ω → header pin 2
• Orange wire: +5 V → 220 Ω → header pin 1
• Black wire: header pin 3 → ground

THRU3 (inverter D)

• Blue wire: pin 8 → 220 Ω → header pin 2
• Orange wire: +5 V → 220 Ω → header pin 1
• Black wire: header pin 3 → ground

THRU4 (inverter E)

• Blue wire: pin 10 → 220 Ω → header pin 2
• Orange wire: +5 V → 220 Ω → header pin 1
• Black wire: header pin 3 → ground

11. Internal MIDI OUT (No DIN Jack)

Use the last inverter (F):

Wiring

• Yellow wire: MatrixPortal TX → 74HC14 pin 13
• Blue wire: 74HC14 pin 12 → internal OUT pad/header

This gives you a clean, buffered logic‑level MIDI OUT.