Schematic Diagram Signal Tracer Kit MODEL ST-751 Elenco Electronics, Inc. 150 W. Carpenter Avenue Wheeling, IL 60090 (847) 541-3800 http://www.elenco.com e-mail: elenco@elenco.com Assembly Instructions Elenco Electronics, Inc. Copyright © 1996 Elenco Electronics, Inc.
Parts List Specifications If you are a student, and any parts are missing or damaged, please see instructor or bookstore. If you purchased this signal tracer kit from a distributor, catalog, etc., please contact Elenco Electronics (address/phone/e-mail is at the back of this manual) for additional assistance, if needed. Injector: Impedance 100W Signal Level 75mV Harmonic Spacing 1kHz Pick Up: Input Impedance 100,000W Gain Adjustable 1 to 50 Resistors Qty.
Troubleshooting Guide Introduction The following guide should help in solving any problems encountered with your signal tracer. First, check your unit for soldering or wiring errors. Next, check the voltage at the emitter of transistor Q1. It should measure between 4.5 to 5.5 volts. If you still have a problem, refer to the following sections for help. Assembly of your signal tracer will prove to be an exciting project and give much satisfaction and personal achievement.
Step-by-Step Assembly Instructions Theory of Operation Refer to Figure 1, install and solder the following resistors. The diagram on the back cover shows the schematic diagram of the signal tracer. Its main component is the dual op-amp LM-358. The first section serves as a squarewave oscillator. Positive feedback is through resistor R3. The frequency of oscillation is controlled by resistor R4 and capacitor C1. These components cause the op-amp to oscillate at a frequency of about 1000Hz.
Testing the Signal Tracer Checking out your signal tracer is fairly easy. You will need a DC voltage source of between 5 to 40V. A 9V battery will do fine. Connect the red alligator clip lead to the positive voltage and the black lead to the negative voltage. The red LED should light up. Next, clip the green lead to the probe tip and connect the earphone to the jack. You should hear a tone in the earphone. Vary the gain control and the tone should vary in amplitude. Obtain an audio amplifier or an AM radio.
Prepare the power cord. On one end, use diagonal cutters to strip off 4” of the gray casing to expose 3 wires (BE CAREFUL NOT TO CUT INTO THE 3 WIRES). Strip off 2” of gray casing off of the other end. Strip 1/4” insulation off of all 6 wires. Label Case Top Nut Jack Cable Notch Jack Notch PC Board Slide the alligator boots onto the 4” wires on the end of the power cord; red boot on the red wire, green boot on the green or white wire, and the black boot on the black wire.
