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Elenco Electronics ST-751, Assembly Instructions Manual, Page: 7 / 12

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Elenco Electronics ST-751 Assembly Instructions Manual Download Page 7

-6-

Figure 6

Install the label onto the case. Be careful to place the label on neatly
and correctly. Peel the backing off the expose the glue.

Place the PC board assembly into the case as shown in Figure 6. Use
two #4 screws to hold the case together. DO NOT OVER-TIGHTEN or
the holes may strip out. Tighten the nut down on the earphone jack.

Press the knob onto the gain control shaft.

Label

Case Top

PC Board

Probe
Notch

Screw

Screw

Cable Notch

Jack Notch

Jack

Nut

This completes the assembly. Your unit is now ready for testing.

Summary of Contents for ST-751

Page 1: ...nc Copyright 2005 1996 by Elenco Electronics Inc All rights reserved 753031 Revised 2005 REV E No part of this book shall be reproduced by any means electronic photocopying or otherwise without written permission from the publisher Assembly Instructions ...

Page 2: ...llow violet orange gold 154700 2 R1 R2 100kW 5 1 4W brown black yellow gold 161000 1 R4 180kW 5 1 4W brown gray yellow gold 161800 1 R7 220kW 5 1 4W red red yellow gold 162200 1 R11 Trim Pot 220kW 191622 Capacitors Qty Symbol Description Part 1 C1 001mF Discap 102 231035 3 C2 C3 C7 1mF Discap 104 251010 4 C4 C5 C6 C9 10mF Electrolytic Lytic 271045 Semiconductors Qty Symbol Description Part 1 D1 Di...

Page 3: ... the flipplet point type and at all times kept clean and well tinned Many areas on the main board are close together and care must be given not to form solder shorts Size and care of the tip will eliminate problems For a good soldering job the areas being soldered must be heated sufficiently so that the solder flows freely Apply the solder simultaneously to the component lead and the component pad...

Page 4: ...R10 1kW 5 1 4W brown black red gold R12 47kW 5 1 4W yellow violet orange gold R13 2 7kW 5 1 4W red violet red gold R14 3 9kW 5 1 4W orange white red gold R15 10kW 5 1 4W brown black orange gold R16 220W 5 1 4W red red brown gold R11 Trim Pot 220kW Figure 1 Top Legend Install and solder D1 the 1N5234 diode Note the diode has polarity as indicated by the band Mount the diode with the band correspond...

Page 5: ...e polarity Place the negative lead in the correct hole as marked on the PC board and part Mount the electrolytics so that they lay on their side Figure 4 Install and solder the transistors with the flat side in the direction shown in Figure 1 Q1 MPS5172 Q2 2N3904 Flat Flat Tubes Install the probe tip Cut a wire to 4 3 4 strip 1 4 of insulation off of both ends Solder one end to point P on the PC b...

Page 6: ... 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 Then solder the 3 clips to the wires Slide the boots onto the clips On the other end of the cable solder the black wire to the hole on the PC board marked GND Solder the green or white wire to the hole marked C Solder the red wire to the...

Page 7: ...ssembly into the case as shown in Figure 6 Use two 4 screws to hold the case together DO NOT OVER TIGHTEN or the holes may strip out Tighten the nut down on the earphone jack Press the knob onto the gain control shaft Label Case Top PC Board Probe Notch Screw Screw Cable Notch Jack Notch Jack Nut This completes the assembly Your unit is now ready for testing ...

Page 8: ... input of the last stage of the amplifier The tone should be heard in the earphone or speaker of the radio Continue injection by moving the tip toward the input and output of each stage Vary the probe gain to prevent overload of the probe If you have an AM radio try injecting the signal into the IF and RF stages The signal tracer produces a 1kHz harmonics which extend into the frequencies of the A...

Page 9: ...tages and for testing of IF circuits in most FM radios The second section of the op amp is designed to be a variable amplifier The input impedance of this amplifier is 100 000W The gain of the amplifier is adjustable between 1 to 50 times depending on the setting of trim pot R11 Resistors R7 and R8 bias the input circuit with C4 serving as a bypass capacitor and C3 the input capacitor The output o...

Page 10: ...with green clip connected to probe tip and the LED is on A Check to see if the IC is in backwards B Must determine if the oscillator or amplifier is at fault If an oscilloscope is available look at the output of the op amp pin 1 There should be 3 to 5V of a 1kHz squarewave If no scope is available put the switch to tip receive position and remove the green alligator clip from the tip Touch the tip...

Page 11: ...ly write or e mail elenco elenco com us and explain 1 the tests that you have made and 2 how the instrument behaved during these tests Our experience has demonstrated that most difficulties can be corrected by an exchange of letters or a phone call If the instrument continues to work improperly and you would like Elenco to locate the problem send the unit along with a 10 00 check to our Service De...

Page 12: ...Elenco Electronics Inc 150 Carpenter Avenue Wheeling IL 60090 847 541 3800 Website www elenco com e mail elenco elenco com Schematic Diagram ...

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