Look for small device circuits where cables break

This device uses a single probe to test whether multiple circuits are connected or disconnected and indicates which end is broken. Components such as 4060 form a 20KHz oscillator, and the connected 100K and 200PF RC components can change this frequency. Each output of the IC, such as Q3, Q4, or Q5, can drive a light-emitting diode or a piezoelectric buzzer to provide the necessary indication. This circuit is installed in a metal box. Hold the cable with one hand and the tester with the other hand, and touch each pin of the cable with the probe in sequence. If the pin is connected, stray capacitance will reduce the tone frequency. Perform the same test on the other end of the cable. The break should be at the end where the frequency is least affected by stray capacitance. Touch one pin of the cable with a probe and touch the other end of the cable with one finger for a one-on-one check. If the cable is intact, the oscillator will stop oscillating. Short circuits in the internal coils of motors and large inductors can also be checked by comparing them with each other.