AM RADIO KIT MODEL AM-780K Assembly and Instruction Manual Elenco Electronics, Inc. ® Copyright © 2010, 1999 by Elenco® Electronics, Inc. All rights reserved. Revised 2010 REV-H No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.
PARTS LIST If you are a student, and any parts are missing or damaged, please see instructor or bookstore. If you purchased this kit from a distributor, catalog, etc., please contact Elenco® Electronics (address/phone/email is at the back of this manual) for additional assistance, if needed. DO NOT contact your place of purchase as they will not be able to help you. RESISTORS Qty. r1 r1 r1 r1 r1 r1 Symbol R6 R4 R2 R5 R1 R3 Value 10Ω 5% 1/4W 150Ω 5% 1/4W 3.3kΩ 5% 1/4W 8.
You Will Need: • 9V Battery • 25 or 30 watt Soldering Iron • Small Phillips and Slotted Screwdrivers • Long Nose Plier • Side Cutters IDENTIFYING RESISTOR VALUES Use the following information as a guide in properly identifying the value of resistors.
WHAT IT IS The AM-780K is a tuned radio frequency (TRF) receiver of the standard AM (amplitude modulation) broadcast frequencies (550kHz - 1600kHz). Easyto-build, using only two integral circuits (IC). in good soldering habits. Above all, take your time and follow these easy step-by-step instructions. Remember, “An ounce of prevention is worth a pound of cure”. Avoid making mistakes and no problems will occur.
CONSTRUCTION Introduction • Turn off iron when not in use or reduce temperature setting when using a soldering station. The most important factor in assembling your AM-780K AM Radio Kit is good soldering techniques. Using the proper soldering iron is of prime importance. A small pencil type soldering iron of 25 - 40 watts is recommended. The tip of the iron must be kept clean at all times and well tinned. • Tips should be cleaned frequently to remove oxidation before it becomes impossible to remove.
ASSEMBLE COMPONENTS TO THE PC BOARD Place a check mark in the box provided next to each step to indicate that the step is completed. D1 - 1N4148 Diode D2 - 1N4148 Diode (see Figure A) R4 - 150Ω 5% 1/4W Res. (brown-green-brown-gold) R2 - 3.3kΩ 5% 1/4W Res. (orange-orange-red-gold) IC1 - 484 / 7642 IC (see Figure B) R1 - 100kΩ 5% 1/4W Res. (brown-black-yellow-gold) C1 - .01μF Discap (103) C3 - .
ASSEMBLE COMPONENTS TO THE PC BOARD C9 - .047μF Discap (473) R5 - 8.2kΩ 5% 1/4W Res. (gray-red-red-gold) R6 - 10Ω 5% 1/4W Res. (brown-black-black-gold) Socket IC 8-pin IC2 - LM-386 IC (see Figure D) C6 - 470μF Electrolytic (see Figure Ca) C7 - 470μF Electrolytic (see Figure C) R3 - Potentiometer Nut & Washer Knob Washer PC Board Nut Solder 5 lugs to PC board. Tuning Capacitor 2 M2.5 x 3.8mm Screws 1 M2.5 x 7.
INSTALL BATTERY HOLDER AND ANTENNA r Bend the leads of the battery holder as shown in Figure H. Fasten the battery holder to the PC board with a 2-56 x 5/16” screw and 2-56 nut. Solder the leads to the PC board pads as shown. r Install the antenna coil as shown in Figure I. 2-56 Nut Battery Holder Figure H Foil Side of PC Board 2-56 x 5/16” Screw Solder Assemble and mount the antenna to the PC board as shown below. r Put the tab of the first holder into the right hole and twist the tab 90O.
ALIGNMENT r Using a small, slotted screwdriver, adjust the trimmer located on the back of the tuning capacitor to minimum capacitance (as shown in Figure J). 3 Leads 4 Leads Location for min. capacitance Figure J r Turn the power OFF. Put a fresh 9V battery into the battery holder and turn the power ON. Adjust the volume to a comfortable level. Tune the dial (around 1000kHz) until a weak station is heard. Carefully slide the antenna coil on its ferrite core until the station is at its loudest.
3. Make sure that all of the parts are placed in their correct positions. Check if the IC, diode and lytic orientations are correct. 4. Use a 2” wire to short capacitor C2 (see Figure M). Turn the volume control up halfway: C2 a) Short by wire, the speaker terminals several times. If you don’t hear tapping from the speaker, check the speaker, battery, battery holder, capacitor C6 and the switch. b) Short by wire, pins 4 and 5 of IC2 several times.
GLOSSARY AGC Automatic Gain Control. FM Frequency Modulation. AF Audio Frequency Frequency Wave or pulse repetition rate. AM Amplitude Modulation Gain Signal multiplication. Amplifier Converts input signal to output. IC Integrated Circuit. Anode The positive terminal of a diode. PC Board Printed Circuit Board. Potentiometer Antenna Any device that either radiates a signal or pulls in a signal. Three-terminal variable resistor, volume control.
Elenco® Electronics, Inc. 150 Carpenter Avenue Wheeling, IL 60090 (847) 541-3800 Website: www.elenco.com e-mail: elenco@elenco.
