General things to check
- Check the IC orientation
- Check if you did not put an IC in the wrong place (mixed up 74hc165 and 74hc595 for example)
- Are the ICs seated correctly in their sockets? No bend legs?
- Try re-installing the firmware from the SD-card
Buttons not working
The 74HC165 ICs are responsible for reading the buttons. If some or all of the buttons are not working, it is most likely due to an error with those ICs.
- check if all 165 ICs have the right orientation and are in the right location of the PCB (and not mixed up with the 595 ICs for example)
- check that all 165 ICs sit tight in their sockets. sometimes a leg can be bend below the ic.
- measure continuity with a multimeter for the following pins:
- pin 2 of each 165 IC should be connected to pin 28 of the AVR
- pin 1 of each 165 IC should be connected to pin 27 of the AVR
- pin 9 of U2 should be connected to pin 29 of the AVR (DIN_DATA)
- pin 10 of U2 is connected to pin 9 of U5
- pin 10 of U5 is connected to pin 9 of U6
- pin 10 of U6 is connected to pin 9 of U12
- pin 10 of U12 is connected to pin 9 of U10
- each of the 165 ICs controls 8 buttons. the groups are the following:
- U2: Seq. buttons 1-8
- U5: Seq. buttons 9-16
- U6: Select buttons 1-8
- U10: Start, Rec, Shift, Voice, Perf., Step, Load/Save
- U12: Voice buttons 1-7 and Copy button
LEDs not working
The 74HC595 ICs are responsible for the LED signals.
...more to come