1. Right after power up, the clock should make a beeping sound. If that does not happen, here are possible causes:
- missing input 5V power; the optional power LED may be useful in this case, turned on when the power is present;
- reset pin may be shorted to ground (the processor won't execute any code);
- processor may not be powered: check that pin 10 has 5V and pin 11 is connected to ground;
- faulty or missing the 16MHz clock for the processor; check crystal connections to the pins; if everything looks good electrically, try to upload a sketch; it that still doesn't work, test by replacing the processor or replacing the crystal;
- buzzer may be disconnected; check connections between processor's pins and buzzer, shorts to the ground, terminal soldering.
2. The display does not light up at all (assuming the display is not defective):
- faults in the connections to the display (right-hand header): look for shorts between neighbor pins in the display header; look for shorts between any signal pins in the display connector and ground;
- output header (left-hand) display header may have shorts between neighbor pins or pins shorted to the ground;
- the board's female connectors may be misaligned (shifted by one) when plugged in the display's male headers.
3. Getting SD card error in "Quote" mode:
- faulty SD card; check the SD card itself by reading it in a PC; must be formatted FAT16 (therefore 2GB or smaller);
- the required text files may be missing; check for their presence in the root directory;
- SD card may not be powered; check 3V3 power on the third pin from the left (second pin from the left is connected to the ground);
- check voltage divider resistors R5, R6, R7 (under the processor) and make sure they are 4K7.
4. Pressing a buttons (Set, Menu or Plus) does not trigger the expected action:
- button itself may be defective, either always open (there is no contact between button's terminals when button is pressed) or always closed (short between terminals); verify with a multimeter that the button works correctly;
- look for potential shorts between the "active" terminal (connected to the processor pins D0, D1 and D2/D3, see schematic) and ground.
5. Communication error when trying to upload a sketch:
- make sure you plugged the FTDI cable/breakout the correct way/orientation, with the Ground/Black terminal to the right;
- check the Rx/Tx connections to the processor (pins 14 and 15); make sure that they are not cut or shorted to the ground;
- "stk500_getsync(): not in sync: resp=0x00 error" usually indicates that the upload speed is incorrect; for the ATmega644P processor, the upload speed must be 38400 (defined as atmega644.upload.speed=38400 in boards.txt); for the ATmega1284P processor, the upload speed is 57600;
- if you get "avrdude: Yikes! Invalid device signature. Double check connections and try again, or use -F to override this check", temporarily modify the signature in file hardware/tools/avr/avr/etc/avrdude.conf with one of these (depending on your processor):
- signature = 0x1e 0x96 0x0a; // for ATmega644P
- signature = 0x1e 0x97 0x05; // for ATmega1284P