Simple crystal oscillator test circuit

This article introduces a simple and easy-to-make crystal oscillator test device. The principle circuit is shown in the attached figure. In the figure, V1 and its peripheral components (including the crystal oscillator under test) together form a capacitive three-point oscillator. When both ends of probes X1 and X2 are connected to the crystal oscillator under test, the circuit oscillates. The oscillation signal is amplified by the V2 emitter follower stage and then output. After being coupled by C4 and voltage doubled and rectified by D1 and D2, it provides a bias current to V3. V3 is turned on and the LED emits light. If the crystal oscillator is defective or open circuit, the circuit will not be able to oscillate, so the LED will not emit light. The device has a simple structure and uses extremely common components. As long as the components are of good quality and the assembly is correct, it can be successful in one go without debugging. The probe can be replaced with two jacks. You can also use test leads or test rods with cables, but the leads should not be too long. This test protocol can test various crystal oscillators with frequencies from 450KHz to 49MHz. The working power supply is recommended to use a 6V laminated battery.