PreenFM > preenfm2 and preenfm3

[Fixed] New Build, buttons do not work

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Hi There -

Just finished my FM2 but have issues. NONE of the buttons work and the encoders just cycle between Engine, Modulation, and Mixer.  The volume knob works and I get sound when I send MIDI over DIN.  My mac does not see the device over USB.

I've attached a picture of my build.

Any thoughts?


I cannot see much on the photo, but double check if you have put the IC's in the right direction. And also that you put the right IC in the right socket.
If this doesnt help, reflow the solder points.

Thanks Patrick for this first help.  :)

If it's really the engine button, check the 4 solder points circled in orange of the attached picture (next time i'll use a thicker brush).
Also pin 9 of the resistor network should be at 3.3V if the button is not pressed and set to GND when button is pressed.

Then you can check the soldering of the GND point near the orange: button and the HC165 CI.
And last (hope not), check the resistor network are in the right direction.

Let me know,


Thanks for the responses :) chips are good, solder is good (I redid the points pointed out by Xavier), button voltages are correct when pressed. Resistor networks are in correctly. I think Xavier is right about it being the Eng button: when I start up by pressing the Op button (for firmware update) it goes to the correct screen (but does not respond then to any buttons).  By the way, I do not get the start up notes playing either.  Here is a link to a better picture:

Have you checked this ?
> "Also pin 9 of the resistor network should be at 3.3V if the button is not pressed and set to GND when button is pressed."
You can test this for all 7 buttons. Look at the red wire to see the currant path.

Also check and redo the middle pin of the encoders.

And the pin 3,5,6 of the CERB40 (see picture above).

Then check carefully the other 74HC165.
Use a sounding 0 ohm detector and look for any shortcut between 2 close point.

And let me know,



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