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 (not included with set but available separately). 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.
The panel PCBs can also be used with our YuSynth range. YuSynth PCBs are better laid out as regards panel wiring but can still take advantage of these breakout PCBs.
This pack contains the following breakout PCBs:
- 7210-704 x 3
- 7210-722 x 3
- 7210-757 x 1
Whilst you can solder wires between the breakout PCBs and the main PCB, we do recommend using our JST cable assemblies. For the Quad Timbre Bank, you will need the following:
- 7210-105 x 3
- 7210-112 x 4
See the Build Guide tab for wiring information on how to use these breakout PCBs with this module.
Guidelines when building a Quad Timbre bank module using our panel PCBs, front and back panels, PCB holder and the MFOS main PCB.
- Assembled MFOS PCB #7210-006
- Front Panel #7210-506
- Back Panel #7210-806
- PCB Holder #7210-906
- 4-Way Pot PCB #7210-704 (4 reqd.)
- 4-Way 1/4" Jack Socket PCB #7210-734 (3 reqd.)
- 12-way Cable Assemble #7210-112 (4 reqd.)
- 5-Way Cable Assembly #7210-105 (3 reqd.)
- PCB Holder Brackets Fixing Kit #7210-181
- PCB Mounting Fixing Kit #7210-182
- Additionally you will need our Switchcraft Jack Sockets #7212-211 (Pack of 10)
This is a more complex module to build but is certainly made easier with our breakout PCBs
Panel PCB Preparation
PCB #7210-704, three of these are used for the 4 banks.
Each of these will be referred to as the Frequency, VCA Level and Resonance PVBs, we marked ours with a 'F', 'V' ad 'R' respectively to aid identification. The first task is to solder the bridges as follows:
- Frequency PCB: solder across C, E & G
- VCA Level PCB: solder across C, E, G, D, F, H
- Resonance PCB: No links
- Solder in JST headers noting that the slots in the socket housing point towards the top of the board on the pot
- Remove any anti-rotation lugs on the pots. Note all pots are 100k linear except for the resonance PCB which are 10k lin.
- Insert pot into bracket and temporarily do up lock nut
- Insert pot with bracket into PCB and solder in position ensuring the pot bracket sits flat on PCB. Only solder the bracket lugs on the bottom of the board
- Repeat for remaining pots
- Remove pot nut
PCB #7210-722, three of these are used for the 11 jack sockets.
Each of these will be referred to as the Input/Output, Banks AB & Banks CD PCBs.
On the Input/Output PCB, solder a wire link between R1 & R3, see the photo below to aid identification. Next solder in the JST housings. Now solder in the jack sockets, we prefer to place the sockets in the aluminium back panel and then place the PCB over the connections before soldering. For the Input/Output PCB, only 3 sockets are used in positions J1, J2 & J3.
PCB #7210-757. This PCB is used for the toggle switches. Like the jack sockets, place the switches into the aluminium back panel, place the PCB over the connections before soldering as this aids alignment.
Next, assemble the front & rear panels along with the mounting brackets / PCB holder and each of the assembled panel breakout PCBs. Note that the VCA level PCB is oriented the other way around to the other two pot PCBs. Do make sure that each PCB goes to the correct group of holes in the panel by checking against the front panel legend.
Here's another view where you can see the mounting brackets more clearly.
Plug in the JST cable assemblies ensuring that the colour sequence is exactly as below. If it differs, check that you have soldered in the JST housings correctly and that the PCBs are the right way around.
Now comes the final task of soldering each of the wires to the respective point as follows:
Where it states Cut, cut the wire close to the header
Also, from the Resonance PCB, wires from the toggle switch PCB are soldered into R3, R6, R9, R12 designations.
VCA Level PCB
Toggle Switch PCB
|3||White||Resonance PCB 'R3'|
|6||Green||Resonance PCB 'R6'|
|9||Grey||Resonance PCB 'R9'|
|12||Red||Resonance PCB 'R12'|
Input/Output Socket PCB
|2||Red||Input Level Pot CW terminal|
|5||Orange||Input Level Pot CCW terminal|
The input level pot wiper is connected to the main PCB X46 pad (thank you to Ian G for pointing this out)
Banks AB Socket PCB
|5||Orange||Designation C1 on Input/Output PCB (pad nearest edge of PCB|
Banks CD Socket PCB
|5||Orange||Designation C1 on Banks AB PCB (pad nearest edge of PCB|
An additional wire is required from C1 (pad nearest edge of PCB) to the 0V on the MFOS main PCB.
Dress the wiring, we use 100mm cable ties
Wiring is now complete except for the +/-12V supply whcih depends on your own system. We solder in a 3-core cable with a plug on the end which we use for power distribution in our racks. Next is a visual inspection and we also apply power before inserting chips to check for correct polarity across one of the IC sockets.
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