The signal tracer may also be utilized as a simple monitor. It has been designed to detect or inject into an audio circuit a specific signal during the repair and for easy fault or problem detection and tracing of equipments. This device will provide benefit and great troubleshooting for audio circuits from the input to the speaker. Signal tracers that utilize LED for displaying digital levels are considered sophisticated types. The device is typically packed into a small, hand-held test probe and the detector is sensitive to amplitude modulation but can also be applied for testing circuits that are using other types of modulation such as FM radios. In general, a signal tracer is a simple device that is mostly powered by a battery which consists of a loudspeaker and an amplifier. It is advised to enclose the circuit in a metal casing or aluminum foil lined plastic case. Since the circuit is a high gain type, proper shielding and grounding is necessary. With this, there will be sufficient harmonics from audio up to hundred kilohertz, which can also be useful in investigating AM radio receivers.
#Circuit board tracer generator
When the SPDT switch is turned to the other side, both transistors will be conducting as a generator of astable square wave.
#Circuit board tracer series
Since the capacitor is in series with the signal, the energy is transferred between the by means of capacitive coupling of the two stages. The 1 nF capacitor at the probe end provides blocking of DC because both the tracer and injector operate at AC source or a 9V or 12V battery source. Both transistors are supplying high gain and both conducts as emitter follower. From the diagram, the switch is in contact with the earpiece circuit while connecting to the collector of the transistor, which means the state of the circuit is in trace mode. To switch between the trace and inject mode, a single pole double throw (SPDT) switch is used. In this circuit, the signal tracer is a low noise, high gain amplifier, with a small speaker for audible monitoring while the signal injector is an audio oscillator that acts as the signal source in the absence of an input signal being acquired. The presence of a fault in the circuit is signified by the disappearance of the signal. The circuit is believed to be working for as long as the signal is still being heard. The signal can be followed around the various components of the radio receiver using the signal tracer. To illustrate the operation of this circuit, it starts by injecting a test signal into the device that is to be tested.