The PCB

The PreenFM2 is an easy to build kit, should take between 2 to 3 houres, less if you’re experienced.

First, please check the BOM and make sure nothing is missing.

 

Then 2 things to take care of :

1 . Don’t mix the 20 pins regular male header with the 20 pins low-profile male and female header. 

PFM2_Headers

2 . Keep in mind that most components will be solder on the front side except : 

The LCD connector
The volume pot
The 4 rotary encoders
The 7 switches

The rest is on the front side. It happened to me to solder the volume pot on the wrong side in the hurry, it was very difficult to unsolder it.

 

OK, that being said, let’s start  by soldering the 9 declouping 100nF  capacitors.

 

DSC00782

 

 

Then you can go with the 330nF that is recommanded in the 7805 regulator spec.

DSC00783

 

After that, you can sodler the resistors, take the resitor sheet :

PreenFM_0010b

 

 

Respecting this order is an easy way to solder them all :

68 DSC00785

220

DSC00790

 

1.8K

DSC00791

 

8.2K

DSC00793

Then the 115K  :

DSC00798

 

And the 1M  :

 

DSC00800

 

And then, you should have 2 10K left :

 

DSC00796

 

 

Now you can put the 2 diodes, D1 is the small red one, D2 the bigger black and white.

Orientation is very important, don’t miss the black ring on D1 that must respect the orientation drawn on the PCB.

 


DSC00803

 

Mind the silver ring on D2: 
DSC00804



And the inductor (looks like a resistor but greener ;-) that is in the plastic bag with the diodes :

DSC00806

 

Then take the 2 resistor networks and put them like on this picture, the orientation is VERY important. The triangle of the 9 pins resistors must be over the left pin of the PCB (the pin that is alone in the white square).

 

DSC00809

 

On the above picture we also added the LED. The minus of the led is specified on the PCB (the right pin).

The minus of the led is the shorter pin.. Give a look at this if you hesitate : http://www.thediyworld.com/How-To-Properly-Use-LEDs.php

Identify-LED-Pinout

 

Now let’s solder the operational amplifer and its 4 plastic capacitors. With the resistors around, it acts as a low pass filter (20Khz).

DSC00811

 

 

And the other DIP8, DIP14 *2, DIP16 *2 and DIP40 sockets. Respect the orientation so that it’s easier to put the ICs in the right orientation too later.

 

DSC00813

 

 

Now you can solder the 3 jumpers.

Take the 20 pins male header you get in the Kit and cut it. Don’t mix with the male and femele LCD connectors :

 

 

DSC00814

 

Jmp1 : The main current pass through this 2 pins. If you want to add a power switch this is the place. In any other case you want to have a connection here.

Jmp2 : This is the current from the USB plug. The 5V from the USB pass through it. If you want to enjoy the midi over USB while using a wall power supply (for exemple to control the PreenFM from an Ipod/Iphone/Ipad), it’s better to open Jmp2. That will avoid the 5V of the USB to be connected to the 5V of the regulator that can be a bit different.

In most case, you want the USB to power the PreenFM2, so the 2 pins must be connected.

 

 

 

DSC00818

 

Jmp3 : if connected, the PreenFM will boot in the DFU (Device Firmware Update) mode integrated in the STM32F4. Usefull to burn the firware for the first time.  After this, the DFU mode can be reached from the surface controle.

 

In the Kit there is a 2 pins right angle header. Spot the 2 pins USB on the PCB. These are the Data- and Data+ of the input USB plug. They will be redirected to the FEZ40 throught the cable we’ll build later.

DSC00822

 

 

 

Now you can take the 6 electrolytic capacitors (2*22uF and 4*220uF). Mind the orientation, all the minus are in the same position.

5 of them are gathered on the left of the PCB.

DSC00823

 

And the last 220uF one on the other side.

DSC00825

 

 

The 4 next steps consist in soldering the variable resisitor for the  LCD contrast, the 2 male connectors for the midi connection, the 5V and the 3.3V regulator :

Variable resistor + 2 * 2 pins male connector (note that your variable resistor may look different – blue and smaller) :

DSC00832

 

The 7805 – check twice it’s actually the 7805 :

 

DSC00834

 

And the LD33 :

DSC00836

 

 

For the USB stick socket, be carefull with the angle. It may be a good idea to solder it withou your usb stick inside. Leave a small additional gap because later you’ll have an encoder bellow that will push a little the Usb stick.

UsbSocketAngle

 

Then you can solder the USB socket for the usb stick and your PCB will look like this :

 

DSC00837

I found it easier to solder the 16 pins male header (LCD connector) at this point – Before the audio jacks are on.

In the kit you’ll find a 20 pins male and femele header. Cut them so that you have a 16 pins male and female header.

DSC00841

 

Flip the PCB over. Make sure it’s totally inserted inside the 16 PCB holes and completely against the PCB then solder it :

DSC00844

Flip the PCB over  again and place the DC connector, the USB and the 2 audio jacks :

DSC00848

 

Then you’re done with this side.

 

The controle surface side is easier. Just be sure that all the components of this side are well in place before soldering.

 

DSC00851

 

Solder the low profile male header to the LCD.

DSC00852

And insert it slowly in the 16 pins female header. In the bottom part use a 2 * 12mm screws + 2* 5mm plastic spacer to mantain the LCD.

DSC00854

And you have you controle surface ready :

DSC00853

 

Now you can put in place the ICs, respect the orientation and don’t swap the 6N137 and the MC3302. The rest cannot be swaped ;-)

Download the zip file example from the download page and extract it to you USB drive on your computer before inserting it.
At the same time you can fill the « pfm2/dx7″ firectory with up to 256 sysex DX7 bank files.
If you receive a CERB40 already flashed check you have the last firmware. If not: download the last firmware from the download page, extract the pfm2_*.bin file in « /pfm2″, then press « Op » button while switching on the PreenFM. Flash it. Et voila.

 

DSC00858

 

 

You have now to connect the CERB40 to the USB connector, use a DIY mini USB connector and 2 wires :

Nothing critical here but soldering this mini male USB is not easy. Maybe the hardest part of the preenFM.

 

MiniUsbConnector

 

If you bought the USB connector on mouser the pin number are like this :

UsbMouser

 

Only the pins 2 and 3 must be soldered and connected to the pins 2 and 3 of the PCB USB slot.

The pin 2 correspond to USB D-
The pin 3 correspond to USB D+
Ground and 5V are passed through the DIP40 pins so they are not part of this cable.

No need to keep a long cable, the wire can be cut at 5cm.

 

DSC00865