Perfboard layout

This chapter provides the complete physical layout for assembling the MIDI Interface on a 2" × 3.5" solderable half‑breadboard perfboard (ElectroCookie style).
It includes:

• Exact placement of the 6N138, 74HC14, 78L05, NPN transistor, resistors, and capacitors
• Placement of all panel headers (MIDI IN, 4× THRU, LED, switch, DC input)
• Power‑rail usage and recommended routing strategy
• A literal, row‑and‑column‑based layout for reproducibility

Perfboard overview

You are using a 2" × 3.5" solderable half‑breadboard perfboard with:

• A center gap between rows E and F for DIP ICs
• Power rails along the left and right edges
• Rows labeled A–J (top to bottom)
• Columns numbered 1–30 (left to right)

For consistency, this manual uses:

• Row A = top edge
• Row J = bottom edge
• Column 1 = left edge
• Column 30 = right edge

ICs straddle the E/F gap.

Note -- I filed the traces off of the bottom power rails so that each of those holes is individual and can be used for the headers.

IC orientation

6N138 placement

Place the 6n138 so that:

• Pins 1-4 sit on E8–E11
• Pins 5-8 sit on F11–F8

74HC14 Placement

Place the 74HC14 so that:

• Pins 1–7 sit on E12–E18
• Pins 8–14 sit on F18–F12

This keeps it to the right of the 6N138 with clean routing to the THRU resistors.

78L05 Regulator

Place 78L04 so that:

• H26 = VIN
• H27 = GND
• H28 = +5 V

Component placement map

Below is the literal placement map for all components.

ICs

• 6N138: E8–E11 / F8–F11
• 74HC14: E12–E18 / F12–F18

Transistor

• NPN (2N3904/2N2222):
  • Collector → near F10/F11 region
  • Base → near F9 (470 Ω resistor connects here)
  • Emitter → ground rail

Recommended location: Rows G–H, Columns 9–11

Resistors

MIDI IN / Optocoupler

• 470 Ω: between 6N138 pin 6 (F10) and NPN base
• 10 kΩ: between NPN collector and +5 V rail
• 1 kΩ: LED series resistor near LED header

MIDI THRU

Place the four 220 Ω resistors in a vertical bank below the 74HC14:

• R1: G13
• R2: G14
• R3: G15
• R4: G16

Each connects from a 74HC14 output to its corresponding THRU header.

Capacitors

Regulator input side

• 0.33 µF: between H26 (VIN) and H27 (GND)
• 10 µF (16 V+): same nodes, placed nearby

Regulator output side

• 0.1 µF: between H28 (+5 V) and H27 (GND)
• 10 µF (10 V+): same nodes, placed nearby

Panel header placement

All panel headers are placed along the bottom edge (Row J) for clean wiring to the enclosure.

Left to Right:

1. MIDI IN Header (3‑pin)
   • J5–J7
2. MIDI THRU Headers (4× 3‑pin)
   • THRU1: J10–J12
   • THRU2: J14–J16
   • THRU3: J18–J20
   • THRU4: J22–J24
3. LED Header (2‑pin)
   • J26–J27
4. Power Switch Header (2‑pin)
   • J28–J29
5. DC Input Header (2‑pin)
   • J30–J31 (or nearest available)

Power rails

Use the built‑in rails:

• Left rail: Ground
• Right rail: +5 V

Connect:

• 78L05 output (H28) → +5 V rail
• 78L05 ground (H27) → ground rail
• 6N138 pin 8 (F8) → +5 V rail
• 6N138 pin 5 (F11) → ground rail
• 74HC14 pin 14 → +5 V rail
• 74HC14 pin 7 → ground rail

Recommended routing strategy

MIDI IN section

• Keep the LED‑side wiring short
• Route the 470 Ω resistor directly to the NPN base
• Keep the 10 kΩ pull‑up close to the NPN collector

THRU section

• Route each 74HC14 output straight down to its 220 Ω resistor
• Then straight to the THRU header pins
• Maintain clean, parallel lines for serviceability

Power section

• Keep regulator capacitors tight to the 78L05
• Use short, direct traces to the rails
• Avoid crossing the logic section with VIN wiring

Final checkpoints

Before soldering the wiring:

• Confirm 6N138 pin 8 is on F8 and goes to +5 V
• Confirm 6N138 pin 5 is on F11 and goes to ground
• Confirm 74HC14 pin 14 is powered and pin 7 is grounded
• Confirm all THRU resistors are 220 Ω
• Confirm the NPN emitter is grounded
• Confirm the LED resistor is 1 kΩ
• Confirm the regulator capacitors are oriented correctly