Erica Synths Pikocore XL DIY Kit Assembly Manual

Schematics Overview

The document includes detailed schematics for the Pikocore XL, outlining the connections and components. Key components include the Raspberry Pi Pico (RPCORE2), various resistors (R1-R28), capacitors (C1-C21), diodes (VD1-VD5), transistors (VT1), potentiometers, and connectors (XS1-XS6).

Important Notes from Schematics:

• The RP board is pre-programmed and ready to use.
• Two options for +5V regulators are present on the PCB: a switching regulator and a linear voltage regulator (LDO). The kit includes components for the linear voltage regulator.
• Specific components (DA2, C14, C15, C16, L1, VD4) should not be populated when using the linear voltage regulator option.
• The document references schematics by Zack Scholl and MegaPCB by Erica Synths.

Assembly Instructions

The assembly process is detailed across several pages, guiding the user through soldering various components onto the PCB.

1. PCB Preparation: Place the Pikocore PCB in a PCB holder or on spacers.
2. Component Placement: Start with lower, horizontally placed components like resistors and diodes. Bend resistor leads and insert them into relevant places according to the part placement diagram. Note the orientation of diodes, matching the white stripe on the PCB to the stripe on the component.
3. Capacitors: Sort ceramic capacitors (100nF, 10nF, 1uF) and populate the 100nF capacitors first, followed by others. Electrolytic capacitors are bipolar; mind their orientation (longer lead is positive, minus stripe indicates negative lead).
4. Voltage Regulator: Install and solder the voltage regulator (LDO), ensuring it touches the heatsink on the PCB.
5. Resistors: Install and solder the remaining vertically placed resistors.
6. Connectors and Jacks: Solder all jack sockets and connectors, ensuring they are properly pushed in and aligned with the silkscreen. Solder one pin first, double-check alignment, then solder the rest. Solder the two-pin male connector for the jumper next to the XS3 jack socket. If using a mono jack for audio output, do not install the jumper.
7. Inspection: Turn the PCB around and inspect solder joints for quality. Remove any excess flux.
8. Cherry Keys: Install and solder the cherry keys and their LEDs. Ensure the LED orientation is correct (longer lead is the anode) and aligned with the PCB silkscreen.
9. Potentiometers: Install and solder all 4 potentiometers.
10. Wiring: Cut the wire into two pieces and solder it to the power switch. Solder the male connectors to the RP board, ensuring alignment and vertical positioning.
11. Jumpers: Solder two "jumpers" on the RP board by placing a solder blob on the SMT polygons indicated in the picture to ensure correct operation.
12. Testing: Test the voltage regulator by using a resistor lead to emulate a closed switch and connecting the power supply. Measure voltage between pins 2 and 3 of the LDO. It should read around 5 volts.
13. Final Assembly: Disconnect the power supply, install the RP board. Power the unit on and check if the LEDs on the cherry keys and RP board light up sequentially.
14. Knobs: Install the knobs onto the potentiometers.

Errata: Swapped Potentiometer Fix

For PCB V2, the Function A and Function B potentiometers may be swapped. To correct this:

1. Cut the traces connecting to the center pin of the two affected potentiometers.
2. Solder a wire from the center pins of these potentiometers to pin 27 and pin 28 of the RP board, as shown in the picture.

Soldering Appendix

For those new to soldering or needing a refresher, it is recommended to watch THT (through-hole technology) soldering tutorials on YouTube.

Key Soldering Tips:

• Apply equal heat to the component and the solder pad on the PCB.
• Keep the soldering iron closer to the pad on the PCB, as it absorbs more heat.
• Optimal soldering temperature is around 320 °C for most parts, and up to 370 °C for larger components like potentiometers and sockets.

Recommended Soldering Sequence:

1. Heat part and pad (2-3 sec).
2. Add solder.
3. Continue heating (1-2 sec).
4. Let cool.

Solder Joint Inspection:

• Perfect: A good solder joint.
• Too much solder: Excessive solder.
• Not enough solder: Insufficient solder.
• Cold joint: A dull, grainy appearance indicating poor heat transfer.
• Too much heat: Can damage components or the PCB.
• Short: Solder bridges connecting unintended points.

Essential Tools for Soldering:

• Soldering Station: Recommended brands include Weller, with cheaper alternatives also available. Ensure it comes with various tip sizes, especially flat, 2mm wide tips.
• Tip Cleaning: Use a damp sponge or professional solder tip cleaners to prevent oxidation.
• Solder Wire: 0.7mm solder wire with flux is recommended for DIY projects.
• Soldering Flux: Paste or pen form can be useful.
• Cutting Pliers: For trimming excess component leads.
• Solder Suction Pump: For removing solder during desoldering.
• PCB Cleaner: For removing excess flux from solder joints.

These tools can be found on major electronic components retailer websites like Mouser and Farnell, as well as local electronics shops.