Elenco Electronics AM-550CK Assembly And Instruction Manual
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Elenco Electronics AM-550CK Assembly And Instruction Manual

Elenco Electronics AM-550CK Assembly And Instruction Manual

Am radio kit dual audio superhet integrated circuit, 7 transistors, 2 diodes
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AM RADIO KIT
MODEL AM-550CK
DUAL AUDIO SUPERHET
INTEGRATED CIRCUIT, 7 TRANSISTORS, 2 DIODES
Assembly and Instruction Manual
ELENCO
®
Copyright © 2016, 2011 by ELENCO
Electronics, Inc. All rights reserved.
REV-A
Revised 2016
753008
®
No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

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Summary of Contents for Elenco Electronics AM-550CK

  • Page 1 AM RADIO KIT MODEL AM-550CK DUAL AUDIO SUPERHET INTEGRATED CIRCUIT, 7 TRANSISTORS, 2 DIODES Assembly and Instruction Manual ELENCO ® Copyright © 2016, 2011 by ELENCO Electronics, Inc. All rights reserved. REV-A Revised 2016 753008 ® No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

  • Page 2: Parts List

    PARTS LIST If you are a student, and any parts are missing or damaged, please see instructor or bookstore. If you purchased this AM radio kit from a distributor, catalog, etc., please contact ELENCO (address/phone/e-mail is at the back of this manual) for ®...

  • Page 3: Parts Identification

    PARTS IDENTIFICATION RESISTORS CAPACITORS SEMICONDUCTORS Resistor Diode LM386 IC 50kW Potentiometer/ Discap Electrolytic Tuning Switch Radial with Nut and Washer Transistor 8-pin Socket COILS Color dot Plastic holders Coil Ferrite core Antenna Assembly Coil MISCELLANEOUS Earphone Knob (dial) Slide Switch Battery Knob (pot) Holder...
  • Page 4 IDENTIFYING RESISTOR VALUES Use the following information as a guide in properly identifying the value of resistors. BAND 1 BAND 2 Multiplier Resistance Tolerance 1st Digit 2nd Digit BANDS Color Digit Color Digit Color Multiplier Color Tolerance Black Black Black Silver ±10% Multiplier...

  • Page 5: General Discussion

    INTRODUCTION The Elenco Dual Audio Superhet 550C AM Radio is This will provide the student with an understanding of ® a “superheterodyne” receiver of the standard AM what that stage has been designed to accomplish, (amplitude modulated) broadcast frequencies. The and how it actually works. After each assembly, you unique design of the Superhet 550C allows you to will be instructed to make certain tests and place the parts over its corresponding symbol in the...
  • Page 6 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 Elenco Dual Audio ® Superhet 550C AM Radio Kit is good soldering techniques. Using the Tips should be cleaned frequently to remove oxidation before it becomes proper soldering iron is of prime importance.
  • Page 7 SEMICONDUCTOR PARTS FAMILIARIZATION This section will familiarize you with the proper method used to test the transistors and the diode. TRANSISTOR TEST Refer to the parts list and find a NPN transistor. Refer Refer to parts list and find a PNP transistor, refer to the Figure A (page 8) for locating the Emitter, Base and Figure B (page 8) for locating the Emitter, Base and Collector.
  • Page 8 SECTION 1A TRANSISTOR AUDIO AMPLIFIER Theory of Operation - The purpose of the Audio Transistor Q4 is a Class A amplifier that drives the base Amplifier is to increase the audio power to a level of transistor Q5 directly. Q5 is a current amplifier that sufficient to drive an 8 ohm speaker.
  • Page 9 ASSEMBLY INSTRUCTIONS - AUDIO AMPLIFIER We will begin by installing resistor R14. Identify the resistor by its color code and install as shown on page 3. Be careful to properly mount and solder all components. Diodes, transistors and electrolytic capacitors are polarized, be sure to follow the instructions carefully so that they are not mounted backwards.
  • Page 10 ASSEMBLY INSTRUCTIONS Figure G Your kit may contain a different type of J1 - Earphone Jack earphone jack. Before installing the jack, with Nut determine which one you have. (see Figure G) GND pad Speaker Foil side Speaker Pad Jack 4”...

  • Page 11: Resistance Test

    You have completed wiring the Transistor Audio Amplifier. We shall proceed in testing this circuit. You will need a Volt- Ohm-Milliammeter, preferably a digital type. STATIC MEASUREMENTS - TRANSISTOR AUDIO AMPLIFIER (SW2 on the top [TR] position) RESISTANCE TEST Adjust the Volt-Ohm-Milliammeter (VOM) to the highest leads.

  • Page 12: Input Bias

    OUTPUT BIAS TEST Adjust your VOM to read 9 volts DC and connect it to test circuit fails this test, turn the power OFF and check that point 8 (TP8) as shown in Figure 5. all of the transistors are correctly inserted in the correct Make sure that the battery, or a 9 volt power supply (if locations.

  • Page 13: Dynamic Measurements

    DYNAMIC MEASUREMENTS DC GAIN Adjust your VOM to read 9 volts DC. Connect the Once again, parallel resistor R13 with resistor R4 as positive lead of the VOM to TP6 and the negative lead shown in Figure 6. The voltage at TP8 should also drop to TP10.
  • Page 14 AC GAIN Connect the VOM and generator to TP6 as shown in the positive lead of your VOM to TP6. Record the AC Figure 7. voltage input to the amplifier here: Turn the power ON. Normally the AC gain is measured at a frequency of 1 kilohertz (kHz).
  • Page 15 AC BANDWIDTH Connect the oscilloscope (set to AC input measurement) waveform on the oscilloscope drops to 0.7 of its original and generator to your circuit as shown in Figure 8. reading, 1.4 Vpp or 2.8 divisions. Use the oscilloscope Set the generator for a frequency of 1kHz and minimum probe to check TP6 to make sure the input voltage did voltage output.
  • Page 16 DISTORTION Connect the generator and oscilloscope as shown in peaks of the sinewave at TP8 are clipped as shown in Figure 8. Set the generator at a frequency of 1kHz, turn Figure 9A. the power ON and adjust the generator output until the Clipped Crossover distortion Figure 9...
  • Page 17 SECTION 1B INTEGRATED CIRCUIT (IC) AUDIO AMPLIFIER For the IC Audio Amplifier, we use the integrated circuit (IC) LM-386. In Figure 11, you can see equivalent schematic and connection diagrams. Figure 12a Dual In-Line and Small Outline Packages Top View Figure 11 Figure 12b To make the LM-386 a more versatile amplifier, two...
  • Page 18 ASSEMBLY INSTRUCTIONS Integrated Circuit C20 - .047mF (473) Discap C18 - 10mF Lytic Capacitor Insert the IC socket into the PC board with the notch in the direction C16 - 10mF Lytic Capacitor shown on the top legend. Solder (see Figure Da) the IC socket into place.
  • Page 19 POWER UP TEST Set your VOM to read the highest possible DC current. necessary. If the current is greater than 25 milliamps, Connect the meter to the circuit as shown in Figure 15. immediately turn the power off. The current should be Make sure that the On/Off switch (SW1) is in the OFF between 3 and 15 milliamps.
  • Page 20 DYNAMIC MEASUREMENTS AC GAIN Connect the VOM and audio generator as shown in of the audio generator until the VOM reads 1 volt AC. Figure 17. Turn the power ON. Normally the AC gain is Leave the audio at this setting and move the positive measured at a frequency of 1 kilohertz (kHz).
  • Page 21 Oscilloscope 10mF Generator Probe TP10 Output Adjust Figure 18 TP10 DISTORTION Connect the generator and oscilloscope as shown in peaks of the sinewave at TP8 are clipped as shown in Figure 18. Set the generator at a frequency of 1kHz, turn Figure 9A.
  • Page 22 SECTION 2 AM DETECTOR AND AGC STAGES THEORY OF OPERATION The purpose of the detector is to change the amplitude The purpose of the automatic gain control (AGC) circuit modulated IF signal back to an audio signal. This is is to maintain a constant audio level at the detector, accomplished by a process called detection or regardless of the strength of the incoming signal.

  • Page 23: Static Measurements

    ASSEMBLY INSTRUCTIONS - DETECTOR C6 - 100mF Lytic (see Figure Da) R8 - 100W Resistor R5 - 27kW Resistor (brown-black-brown-gold) (red-violet-orange-gold) T3 - IF Coil (black) T1 - IF Coil (yellow) TP5 - Test Point Pin TP3 - Test Point Pin (see Figure F) (see Figure F) C15 - .001mF Discap...

  • Page 24: System Check

    DYNAMIC MEASUREMENTS DETECTOR AND ACG TEST Turn the power OFF and connect the VOM and RF until the voltage at TP3 just starts to drop. This point is generator as shown in Figure 21. Set the VOM to called the AGC threshold with no IF gain. Make a note accurately read 2 volts DC and set the output of the RF of the amplitude setting on the RF generator here: generator for 455kHz, no modulaton, and minimum...
  • Page 25 SECTION 3 SECOND IF AMPLIFIER THEORY OF OPERATION The purpose of the SECOND IF AMPLIFIER is to The gain at 455kHz in the second IF amplifier is fixed by increase the amplitude of the intermediate frequency (IF) the AC impedance of the primary side of transformer T3, and at the same time provide SELECTIVITY.
  • Page 26 STATIC MEASUREMENTS Q3 BIAS With the power OFF, connect the negative lead of your emitter of Q3 should be approximately 1 volt. If your VOM to any ground and the positive lead to the emitter reading is different by more than 0.5 volts, turn off the of Q3 as shown in Figure 24.

  • Page 27: Bandwidth Test

    BANDWIDTH TEST With the power OFF, connect your equipment as shown Now increase the frequency of the RF generator past in Figure 26. Turn the power ON and adjust the RF the peak to a point where the signal drops to 0.707 of generator for 0.4Vpp at the cathode of D1.
  • Page 28 STATIC MEASUREMENTS Q2 BASE BIAS With the power turned OFF, reconnect your VOM to test voltage should be approximately 1.5 volts. If your circuit point 3 (TP3) as shown in Figure 20. Set the VOM to fails this test, turn the power OFF and check Q2 and R6. read 2 volts DC accurately and turn the power ON.
  • Page 29 SECTION 5 MIXER AND OSCILLATOR THEORY OF OPERATION In a superheterodyne type receiver the radio wave at the frequencies except those near 455kHz. T1 also couples antenna is amplified and then mixed with the local the 455kHz signal to the base of Q2 to be processed by oscillator to produce the intermediate frequency (IF).
  • Page 30 3 Wire Type Antenna Assemble it to the PC board as shown below. Mount the antenna assembly to the PC board. Solder the 3 colored wires to the PC board. Wire A (red) to the hole marked “3”. Put the tab of the first holder into the right hole and twist the tab 90°.
  • Page 31 PC Board Stand Insert the PC board into the stand as shown. Figure N STATIC MEASUREMENTS Q1 BIAS With the power turned OFF, connect the VOM to your TP1 should be 1.6 volts. If the voltage in your circuit circuit as shown in Figure 28. Connect a clip lead from differs by more than 0.5 volts, leave the power ON and test point two (TP2) to the collector of Q1.
  • Page 32 DYNAMIC MEASUREMENTS OSCILLATOR CIRCUIT With the power turned OFF, connect the oscilloscope to wave. The frequency of the sine wave should change the circuit as shown in Figure 29. Set the oscilloscope for when capacitor C1 is turned. If your circuit fails this test, a vertical sensitivity of 1 volt/division and turn the power turn the power OFF and check components Q1, C1, C2, ON.

  • Page 33: Antenna Alignment

    SETTING OSCILLATOR RANGE With the power turned OFF, connect the equipment to the Oscillator trimmer Antenna trimmer circuit as shown in Figure 30. DO NOT connect the clip lead from TP2 to Q1. Set the RF generator at 540kHz, 400Hz 80% modulation, and a low level of output. Turn 3 Leads the tuning capacitor fully counter-clockwise.
  • Page 34 AM ALIGNMENT WITH NO TEST EQUIPMENT It is best to use an earphone for this alignment their broadcast frequency is announced. If no stations procedure. Rotate the tuning knob fully counter- are present at the low side of the AM band, adjust L2 clockwise and place the label on the knob with the white until a station is heard.
  • Page 35 AM-550CK RADIO BAFFLE NOTICE: Keep the box the kit came in. After you have completed the radio and it operates satisfactorily, you may want to install a baffle to improve the sound. The final step in the radio kit will be to assemble and attach a baffle to the speaker. You will need to remove the baffle located in the bottom of the box.

  • Page 36: Schematic Diagram

    SCHEMATIC DIAGRAM ELENCO ® 150 Carpenter Avenue ● Wheeling, IL 60090 (847) 541-3800 ● Website: www.elenco.com ● e-mail: elenco@elenco.com...

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