Having trouble using Adafruit LM3671
Power supplies sometimes buzz when they are run under low load. This situation can also cause the blinking you described. You can try a number of experiments:


Try running the LM3761 circuit you built on batteries. (3 AA cells might be a good start. Just be sure not supply the LM3671 with more than 5.5V!) See if the blinking stops.
Put a 150 Ohm, 1/4 W resistor in parallel with your circuit. (You can use a lower-valued resistor as long as it can handle the power.) Alternatively, try the power supply on another circuit or device that requires more current. If the buzzing changes in pitch or disappears, you may need to find a different power supply.
Try a different power supply and see if the blinking stops. If you have a bench supply, it is likely to behave more reliably under low load than a wall wart.