LM386 Audio signal tracer RF Probe Amplifier

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The LM386 Audio signal tracer RF Probe Amplifier circuit diagram for maintaining preamplifier, power amplifiers and even RF devices. As a probe of audio signal and RF, can make maintenance of equipment such as amplifiers, preamplifier, radios, car audio, transmitters, recorders, televisions and more. The basic operation is to follow the audio signal to a point where it is not available or is undergoing any changes that should not occur.

About circuit audio signal and RF follower for bench maintenance

To learn how to use this tool, I suggest you download this PDF of the Newton C. Braga (Portuguese language) – Using test instruments measure.

Circuit Audio And Rf Signal Investigator With Lm386 - Tool For Maintenance Of Audio Equipment
Circuit Audio And Rf Signal Investigator With Lm386 – Tool For Maintenance Of Audio Equipment

The operation is simple, in two functions:
RF function: the signal will pass through D2, C4 and R1, which form an AM Demodulator circuit, to detect defects in Radio Frequency circuits, the audio will be demodulated and can be heard on the loudspeaker!
AF function: the signal will stop passing through the Germanium diode D2, so you can hear the audio signal amplifier on the loudspeaker! The capacitor C5 prevents any DC component from going to the device being tested. To control the volume, we use a potentiometer of 47K. The overall gain of the Lm386 is set to 200, if you wish you can add a potentiometer in parallel with C3 to gain control of the Lm386. The network formed by C7 / R2, guarantees stability to the Amplifier and avoids RF interference.
To power the circuit we use a 9 Volt battery, so it becomes portable, also a 9 Volt DC power supply can be used.

Circuit diagram of the audio and RF Signal investigator

The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram
The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram

Suggested printed circuit board for mounting of the circuit

Pcb Printed Circuit Board. The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram
Pcb Printed Circuit Board. The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram
Pcb Printed Circuit Board Component View. The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram
Pcb Printed Circuit Board Component View. The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram
Pcb Printed Circuit Board Component Silk. The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram
Pcb Printed Circuit Board Component Silk. The Lm386 Audio Signal Tracer Rf Probe Amplifier Circuit Diagram

BOM for assembling the Audio and RF Researcher with LM386

Part Value
Resistors 1/4 Watt 5%
R1, R3 470K – Yellow, Violet, Yellow, Gold
R2 10 – Brown, Black, Black, Gold
Capacitors
C1,C6 470µF/25V — Electrolytic Capacitor
C2 100nF — Ceramic Capacitor
C3, C5, C8 10µF / 25V — Electrolytic Capacitor
C4, C9 1nF — Ceramic Capacitor
C7 47nF — Polyester or Ceramic Capacitor
Semiconductors
D1 1N4004 or equivalent – Silicon rectifier diode
D2 1n34 or equivalent – Germanium Diode
IC1 LM386N – Audio amplifier integrated circuit
Connectors
IN (CN1) Terminal block 3 pin 5.08 mm – Probe connector for RF or Audio signal input.
OUT (CN2) Terminal block 2 pin 5.08 mm — Connector for the speaker.
Miscellaneous
J1 Power jack, connect external power supply (optional).
P1 10K — Potentiometer
BAT 9V — Connect 9-Volt Battery
Solder, Wire, PCB, Box, Probe, etc.

Download the files for assembling the Signal Tracer – PDF, printed circuit board, circuit schematic, component layout and silk screen, LM386 Datasheet.

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