This audio quartz crystal tester circuit is designed to test quartz crystals using audio signal. Using this This is possible if the output frequency band is brought to the audio band audio band using demultiplication with a circuit like the diagram below.
Crystal tested is connected to input terminals, and S2is positioned as shown in Figure. Crystal frequency is divided by IC1 and, depending on the position of S2, one of 4060's output control transistor T1 through R2 which drive a speaker. For crystals <1 MHz, the division factor is 128, the crystals in the range 1-10 MHz, the factor is 4096, and for crystals> 10 MHz, the division factor is 8192.
When tested crystal is below 10 MHz S2a and D2 takes down voltage up to 4.7 V.
If using a power source instead of a 9 V battery, we recommend a 12 V / 50 mA (D2 must be 6.8 V).