Introduction

We find that wiring a MFOS PCB to the front panel controls is both time consuming and often detracts from the overall finish. We are not able to alter the MFOS PCBs to make panel wiring easier so we approached the problem from a different angle. We chose to mount the front panel controls on a mini PCBs (breakout boards) that take the panel controls to a JST type XH socket into which is plugged a lead. This lead is then dressed to the main MFOS PCB (or sometimes to other panel controls) and soldered into the respective pads. Many breakout boards have solderable jumpers for making common connections as well as thin tracks to cut where panel mounted resistors need to be connected inline with say a pot wiper. MFOS projects may require multiple breakout boards so we bundle these altogether and offer them in one ST Synth Panel Breakout PCB Set. The pack description will further describe the wiring colour code and what if any links need to be made or cut.

This method does have other advantages other than just time saving and appearance:

• Time saving
• Neater more professional appearance - improves resale value
• Takes care of common connections between panel components
• Has space to accommodate panel mounted resistors and capacitors
• Can improve reliability - have you tried soldering a diode, LED and a wire to one pin on a toggle switch on the 16-step sequencer?
• Makes fault finding easier

If you have any reservations about using connectors, then simply solder wires direct to the breakout boards. Takes longer but you still get all of the other advantages.

The boards are designed to fit our front panel component spacing so you will see references to pitch and whether it is in the 'x' or 'y' or both direction. At the time of writing, there was 30+ breakout boards developed for pots (using pot brackets), sockets (jack and banana), switches and LEDs. Whilst these will not take care of every panel component on over 40 MFOS projects, it will go a long way to achieving it. As we work through making up each MFOS project with these breakout boards, we will see where improvements can be made or even create more breakout boards to provide the best possible solution.

Specific Information on the 7-Pot Panel PCB (28y Pitch). Board size: 194x28mm

7210-701 accommodates 7 of our commercial grade synth pots along with our pot mounting brackets on a 28mm vertical pitch. Click the schematic image above to see the circuit for this board. This board is designed specifically for the 7-seg Envelope Generator module although can be used for non-Soundtronics projects as well. Each of the pot sliders are connected to J1. The CCW terminals are commoned together (ground 0V) and wired to J2 & J3. The CW pot terminals are wired to both J2 & J3 where J3 is wired to the MFOS main PCB. As the 7-seg Envelope Generator has two banks of 7 pots, two panel PCBs are needed whcih we will call the Threshold PCb and the Sustain PCB. J2 is used to connect both panel PCBs together in order to common up the CW terminals, you can fit the socket on say the Threshold PCB and solder the wires direct to the Sustain PCB. Note: J3 is not needed on the Sustain PCB. Two further sockets are included, J4 & J5 which are wired to solder pads X1:X8 and X9:X16 respectively as a way of patching other panel components to the MFOS main PCB. Further details of this patching can be found in the ST Synth Panel Breakout PCB Set for the 7-Segment Envelope Generator MFOS project. However, with a maximum of 32 connections over the 2 panel PCBs available, there is capacity to wire all of the remaining panel components to the panel PCBs for a tidy solution.

Note PCB 'X' pad numbers do not relate to the MFOS panel wiring 'X' numbers.

Two ground connection pads are provided for connecting the board to 0V (ground).

Assembly

1. Solder in the sockets noting that the slots in the socket housing point towards the top of the board
2. Remove any anti-rotation lugs on the pots
3. Insert pot into bracket and temporarily do up lock nut
4. Insert pot with bracket into PCB and solder in position ensuring the pot bracket sits flat on PCB.
5. Repeat for remaining pots
6. Rev 1 PCBs Kludge: Solder a bridge between P7 CCW terminal and P7 bracket. Rev 2 boards
7. Remove pot nuts
8. Install assembled board into panel front and tighten pot nuts (washers not required)
9. Plug in cable assemblies and wire to main MFOS PCB / other panel PCB as required

PCB Rev 1 Kludge, Rev 2 PCBs do not need this

Wiring Colour Code

Pin 1 (black wire) is on the left hand side of the connector.

It is always worth checking the wire colour sequence to ensure it matches the above just in case there has been a mistake at the factory in the assembly of the cable.

Typical examples of projects that use this board: 7-Segment Envelope Generator