MRG FOLD (Bare PCB) Assembly Guide

This is the assembly guide for the MRG Fold bare PCB build. If you have a SMD presoldered PCB, check the MRG FOLD presoldered assembly guide.

Its build should be considered of medium difficulty given the number of components and steps required.

Theory of operation:

  1. If you bought the PCB+Panel only, acquire needed components (See Bill of Materials. All components used in this guide are already included in the full DIY kit.
  2. Build the Main PCB.
  3. Build the Front PCB.
  4. Install the front panel.

Main PCB build

fold pcb

Step A1. Start by soldering all horizontal resistors and the two 5V1 Zener diodes.

fold pcb

Step A2. Solder all ceramic capacitors.

fold pcb

Step A3. Solder the two voltage regulators.

fold pcb

Step A4. Solder the 10-pin header Eurorack connector.

fold pcb

Step A5. Solder the two 22uF electrolytic capacitors.

fold pcb

Step A6. Solder the TL074, TLV274 and the TL072 opamps. If desired, you can solder IC sockets at this stage (two 14-pins and one 8-pins), and insert the ICs in the sockets later on.

fold pcb

Everything apart from the two 14-pin headers are soldered on the board now. It is time to solder the front PCB.

Front PCB Build

Step C1. Check the alignment of the PCB (label U1 is the top row), arrange the jack sockets and the potentiometers.

fold pcb

Step C2. Solder the components. Tip: in order to be sure to align the components to the front panel, install the front panel as in photo below and solder the components on the back.

fold pcb

Step C3. Solder the socket headers. Tip: In order to align the Main PCB's pin headers to the Front PCB's socket headers, assemble the two PCBs together, as in picture, and solder them in place.

fold pcb

Congratulations! The build is nearly done. All that's left is installing the front panel.

Final Module Assembly

All that's left now is to install the front panel, using nuts and washers to keep it attached, and adding the knobs to the potentiometers.

fold pcb


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Bill of Materials

This is the required bill of materials if you bought the PCBs+Panel+IC only. All components listed below are already included in the full DIY kit.

Resistors usually included in the kit are usually Multicomp MF12 Series.

Note: The folding circuit (centered around the TLV274IN) is highly sensitive to resistor values. The use of 1% tolerance resistors is required.

Component Quantity Notes

ICs:

TL074BCN1PDIP
TL072BCP1PDIP
TLV274IN1PDIP

Resistors:

4701
7K51
11K4
13K2
15K1
18K1
20K1
24K1
51K1
56K1
91K1
100K3
110K2
160K1
220K1
360K3

Ceramic Capacitors:

100nF (104) 7MLCC 5mm pitch
1uF (105) 1MLCC 5mm pitch
10p (100) 3MLCC 5mm pitch

Other Capacitors:

22uF Electrolitic Capacitor 2 Rubycon 25ZLG22MEFC5X7

Other Components:

5V1 Zener 2 DO-35
L78L05 1 5V Voltage Regulator
L79L05 1 -5V Voltage Regulator
14 Pin 2 Row Header22x7 2.54mm pitch
14 Pin 2 Row Socket22x7 2.54mm pitch
10 Pin 2 Row Header12x5 2.54mm pitch
B100K4Alpha 9mm T18 Potentiometer
PJ398SM 3.5mm Jacks4"Thonkiconn"