Elenco Electronics TCT-255K Guía del usuario

MULTI-NETWORK CABLE TESTER KIT

MODEL TCT-255K

Elenco Electronics, Inc.

Assembly and Instruction Manual

GENERAL DISCUSSION

You can see a block diagram of the TCT-255 in Figure 1 below.

The TCT-255 Cable Tester has five basic blocks:

1. Power Supply

It powers all of the circuits of the tester (not including the terminator). The power supply has a low battery

indicator (less than 7.5V) and a circuit to disconnect power 30 - 50 seconds after the last push on the

test switch.

2. Oscillator

Uses a 555 timer IC with two resistors and one capacitor. They control the free running frequency and

duty cycle.

3. Step Pulses with Counter

The outputs change by the positive pulses from the test button switch.

4. Switches and LED Indicator

It includes eight electronic switches for operating the indicators (16 LEDs).

5. Terminator

Connected to cable under test. Identifies the polarity signals.

Cable Tester TCT-200 Terminator LD-100

Figure 1

COUNTER SWITCHES

INPUT & OUTPUT

CONNECTORS

INPUT & OUTPUT

CONNECTORS

STEP PULSES

OSCILLATOR LED

INDICATOR

CIRCUIT

IDENTIFY

POLARITY

POWER

SUPPLY

-1-

The TCT-255 Cable Tester is a convenient instrument

for testing different unshielded wiring schemed

communication cable with RJ-11 and RJ-45

connectors and coax cable. This tester can be used

for testing cables before and/or after they are

installed. The tester offers easy operation by having

to push only one button.Testing status is indicated by

multiple LEDs and an auto power-off function

maximizes battery life.

The unique design of the TCT-255 allows you to

place the parts over their corresponding symbol in

the schematic drawing on the surface of the PC

board during assembly. This technique maximizes

the learning process while keeping the chances of

an assembly error at a minimum. It is very

important, however, that good soldering practices

are used to prevent bad connections.

The actual assembly is broken into SEVEN

SECTIONS. After each assembly, you will be

instructed to make certain tests and measurements

to prove that each section is functioning properly.

The theory for each section, or stage, should be

read before the test is started. This will provide the

student with an understanding of what that stage

has been designed to accomplish, and how it

actually works. If a test fails to produce the proper

results, a troubleshooting guide is provided to help

you correct the problem. For testing you need to

have only a voltmeter for measuring DC and AC.

INTRODUCTION

IDENTIFYING RESISTOR VALUES

Use the following information as a guide in properly identifying the value of resistors.

IDENTIFYING CAPACITOR VALUES

Capacitors will be identified by their capacitance value in pF (picofarads), nF (nanofarads), or mF (microfarads). Most

capacitors will have their actual value printed on them. Some capacitors may have their value printed in the following

manner. The maximum operating voltage may also be printed on the capacitor.

Second Digit

First Digit

Multiplier

Tolerance The letter M indicates a tolerance of +20%

The letter K indicates a tolerance of +10%

The letter J indicates a tolerance of +5%

FortheNo.01234589

Multiply By 1 10 100 1k 10k 100k .01 0.1

Multiplier

Note: The letter “R” may be used at times

to signify a decimal point; as in 3R3 = 3.3

BANDS

12 Multiplier Tolerance

103K

100

Maximum Working Voltage

The value is 10 x 1,000 = 10,000pF or .01mF 100V

-2-

-3-

CONSTRUCTION

Introduction

Assembly of your TCT-255 Multi-Network Cable Tester Kit will prove to be an exciting project

and give you much satisfaction and personal achievement. If you have experience in soldering

and wiring techniques, then you should have no problem with the assembly of this kit. Care

must be given to identifying the proper components and 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.

Safety Procedures

• Wear eye protection when soldering.

•

Locate soldering iron in an area where you do not have to go around it or reach over it.

• Do not hold solder in your mouth. Solder contains lead and is a toxic substance. Wash your

hands thoroughly after handling solder.

• Be sure that there is adequate ventilation present.

Assemble Components

In all of the following assembly steps, the components must be installed on the top side of the

PC board unless otherwise indicated. The top legend shows where each component goes.

The leads pass through the corresponding holes and the board is turned to solder the

component leads on the foil side. Solder immediately unless the pad is adjacent to another

hole which will interfere with the placement of the other component. Cut excessive leads with

a diagonal cutter. Then, place a check mark in the box provided next to each step to indicate

that the step is completed. Be sure to save the extra leads for use as jumper wires if needed.

Soldering

The most important factor in assembling your cable tester 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. Many areas on the PC 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 on the PC board so that good solder flow will occur. Be sure that the lead extends through

the solder smoothly indicating a good solder joint. Use only rosin core solder of 63/37 or

60/40 alloy.

DO NOT USE ACID CORE SOLDER! Do not blob the solder over the lead because this can

result in a cold solder joint.

Heat Sinking

Electronic components such as transistors,

IC’s, and diodes can be damaged by the heat

during soldering. Heat sinking is a way of

reducing the heat on the components while

soldering. Dissipating the heat can be

achieved by using long nose pliers, an alligator

clip, or a special heat dissipating clip. The heat

sink should be held on the component lead

between the part and the solder joint.

Mount Part Bend Leads to Hold Part Solder and Cut Off Leads

Foil Side

Rx - 100W5% 1/4W Resistor

(brown-black-brown-gold)

Heat Sink (this can be ordered as part of Elenco’s Solder Ease

Kit Model SE-1).

Soldering Iron

Solder

Heat Sensitive

Component (Diode)

PC Board

Figure 6

-4-

What Good Soldering Looks Like

A good solder connection should be bright, shiny,

smooth, and uniformly flowed over all surfaces.

Soldering a PC board

1. Solder all components

from the copper foil side

only. Push the soldering

iron tip against both the

lead and the circuit board

foil.

2. Apply a small amount of

solder to the iron tip. This

allows the heat to leave

the iron and onto the foil.

Immediately apply solder

to the opposite side of the

connection, away from

the iron. Allow the heated

component and the circuit

foil to melt the solder.

3. Allow the solder to flow

around the connection.

Then, remove the solder

and the iron and let the

connection cool. The

solder should have flowed

smoothly and not lump

around the wire lead.

Here is what a good

solder connection looks

like.

Types of Poor Soldering Connections

1. Insufficient heat - the

solder will not flow onto

the lead as shown.

2. Insufficient solder -

let the solder flow over

the connection until it is

covered. Use just

enough solder to cover

the connection.

3. Excessive solder -

could make

connections that you

did not intend to

between adjacent foil

areas or terminals.

4. Solder bridges - occur

when solder runs

between circuit paths

and creates a short

circuit. This is usually

caused by using too

much solder. To correct

this, simply drag your

soldering iron across

the solder bridge as

shown.

A poorly soldered joint can greatly affect small current flow in circuits and can cause equipment failure. You can damage

a PC board or a component with too much heat or cause a cold solder joint with insufficient heat. Sloppy soldering can

cause bridges between two adjacent foils preventing the circuit from functioning.

Solder Soldering Iron

Foil

Solder

Soldering Iron

Foil

Component Lead

Soldering Iron

Circuit Board

Foil

Rosin

Soldering iron positioned

incorrectly.

Solder

Gap

Component Lead

Solder

Soldering Iron

Drag

Foil

TROUBLESHOOTING

1. One of the most frequently occurring problems is poor

solder connections.

a) Tug slightly on all parts to make sure that they

are indeed soldered.

b) All solder connections should be shiny.

Resolder any that are not.

c) Solder should flow into a smooth puddle rather

than a round ball. Resolder any connection that

has formed into a ball.

d) Have any solder bridges formed? A solder

bridge may occur if you accidentally touch an

adjacent foil by using too much solder or by

dragging the soldering iron across adjacent foils.

Break the bridge with your soldering iron.

PARTS LIST - SECTION A

RESISTORS

Qty. Symbol Description Color Code Part #

2 R12, R17 1kW5% 1/4W brown-black-red-gold 141000

1 R16 5.6kW5% 1/4W green-blue-red-gold 145600

1 R15 12kW5% 1/4W brown-red-orange-gold 151200

1 R9 3.3MW5% 1/4W orange-orange-green-gold 173300

CAPACITORS

Qty. Symbol Value Description Part #

1 C2 22mF Electrolytic Radial 272244

SEMICONDUCTORS

Qty. Symbol Value Description Part #

1 D17 1N4001 Silicon Diode 314001

1*1N4736 Zener Diode 6.8V 1W 314736

1 D18 1N5235 Zener Diode 6.8V 0.5W 315235

2 Q2, Q3 2N3904 Transistor NPN 323904

1 Q1 2N3906 Transistor PNP 323906

1 D19 LED Red 350003

1 U4 40106 Integrated Circuit (IC) Hex Inverter 330106

MISCELLANEOUS

Qty. Symbol Description Part #

1 PC Board Tester TCT-200 517041

1 SW1 Switch Push Button DPDT 540203

1 Battery 9V 590009

1 Battery Snap 9V 590098

1 Spacer 624018

1 U4 Socket IC 14-pin 664014

1 Tubing #20 1/2” 890020

1 Solder 9ST4

* Packaged in a separate bag, used for testing only.

SECTION A

Power Supply

PARTS IDENTIFICATION

Integrated Circuit (IC)

-5-

Resistor DiodesElectrolytic Transistor LED

IC Socket 14-pin

PC Board (Tester)

Switch Push Button

Epoxy

Zener

Battery Snap Spacer

Tubing

Figure B

Mount the LED with the tubing and

plastic spacer to the PC board as

shown. Note the flat side of the

LED and the PC board marking.

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD

In all of the following steps the components must be installed on the top legend side of the PC board. The

board is turned to solder the component leads on the foil side.

R17 - 1kW5% 1/4W Resistor

(brown-black-red-gold)

(see Figure A)

D19 - LED Red

Tubing

Spacer

(see Figure B)

R9 - 3.3MW5% 1/4W Resistor

(orange-orange-green-gold)

(see Figure A)

Q2 - 2N3904 Transistor NPN

(see Figure C)

D17 - 1N4001 Diode (epoxy)

(see Figure D)

Q3 - 2N3904 Transistor NPN

(see Figure C)

U4 - 14-pin IC Socket

U4 - 40106 IC Hex Inverter

(see Figure E)

SW1 - Push Button Switch

(see Figure F)

R16 - 5.6kW5% 1/4W Resistor

(green-blue-red-gold)

(see Figure A)

C2 - 22mF Electrolytic

(see Figure G)

R15 - 12kW5% 1/4W Resistor

(brown-red-orange-gold)

(see Figure A)

R12 - 1kW5% 1/4W Resistor

(brown-black-red-gold)

(see Figure A)

D18 - 1N5235 Zener Diode 0.5W

(see Figure D)

Battery Snap

(see Figure H)

Q1 - 2N3906 Transistor PNP

(see Figure C)

Figure A

Mount the resistor

flat against the PC

board as shown.

Figure D

Diodes have polarity. Mount the

diodes in the direction marked on

the PC board as shown.

Polarity

Marking

Polarity

Marking

Epoxy

Zener

-6-

Figure F

IMPORTANT!!! Mount the push button

switch as shown. The circle MUST be

facing the other direction from the marking

“SW1” on the PC board.

Figure G

Electrolytic capacitors have polarity. Be sure

to mount them with the negative (--) lead

(marked on the side) in the correct hole.

Polarity

Marking

Flat Side Spacer

LED

Tubing

Figure C

Mount the

transistor to

the PC board

noting the flat

side.

Flat Side

Figure E

Insert the IC socket into the PC board with the

notch in the direction shown on the top

legend. Solder the IC socket into place.

Insert the IC into the socket with the notch in

the same direction as the notch on the socket.

Notch

Marking

Figure H

Mount the battery

snap as shown.

The black (--) lead

goes to --B and

the red (+) lead

goes to +B.

Circle

Red Lead

Black Lead

(--) (+)

1/8”

SECTION A - POWER SUPPLY

When the SW1 (test button) is pushed, capacitor C2

(see schematic diagram, Figure 1) is charged to the

battery voltage. Transistor Q1 turns on and all of the

circuits in the tester are powered. If you don’t push

SW1, capacitor C2 begins discharging. When the

voltage on C2 is less than 0.7V, transistor Q1 and

the power turn off after 30-50 seconds.

When the voltage of the battery is less than 7.5V,

transistors Q2 and Q3 turn on and LED D19 (Low

Battery) lights. The diode D17 protects the tester

from wrong polarity input voltage.

-7-

1. Connect the battery to the battery snap.

2. Set the voltmeter to read 20VDC and connect the

COM lead to the negative (--) side of the battery

and the V lead to the positive (+) side of the

battery as shown in Figure 2. The meter should

indicate 9-10VDC. Push switch SW1.

Remove the V lead from the positive (+) side of the

battery and move to pad of pin 4 of IC U5. The

meter should indicate the same voltage, but after

30-50 seconds, the voltage should drop to 0V.

4. Push the switch SW1 again. The meter should

indicate the same voltage as in step 2. If not:

a) Check that the battery snap is connected

with the the right polarity as shown in the

assembly instructions.

b) Check that the transistor Q1 is 2N3906 and

mounted with the emitter, base and collector

leads as shown in the assembly instructions.

c) Check that R9, R12 and C2 are the correct

values.

d) Check that D17, D18, C2, U4 and SW1 are

installed as shown in the assembly

instructions.

5. Bend the zener diode 1N4736 (6.8V 1W, located

in a separate bag) as shown in Figure 3.

Push the switch SW1 again and short the battery

by the zener diode for 1-2 seconds (the side with

the band should be touching the “+” terminal of the

battery, see Figure 2). LED D19 (Lo Batt.) should

be lit. Remove the zener diode and the LED should

turn off. If not:

a) Check that the transistors Q2 and Q3 are

2N3904 and mounted as shown in the

assembly instructions.

b) Check zener diode D18 and LED D19. Be

sure that they are installed as shown in the

assembly instructions.

c) Check that resistors R15, R16 and R17 are

the correct values.

Remove the battery from the battery snap and

the leads from the tester.

TESTING

Figure 1

Figure 3

0.5” - 0.6”

VCOM

VDC +

Figure 2

PARTS LIST - SECTION B

RESISTORS

Qty. Symbol Description Color Code Part #

1 R13 18kW5% 1/4W brown-gray-orange-gold 151800

1 R14 100kW5% 1/4W brown-black-yellow-gold 161000

CAPACITORS

Qty. Symbol Value Description Part #

1C3 1mF Electrolytic Radial 261047

SEMICONDUCTORS

Qty. Symbol Value Description Part #

1 U5 555 Integrated Circuit (IC) 555 Timer 330555

MISCELLANEOUS

Qty. Symbol Description Part #

1 U5 Socket IC 8-pin 664008

SECTION B

Oscillator

PARTS IDENTIFICATION

-8-

Resistor

Integrated Circuit (IC)

Electrolytic IC Socket 8-pin

Figure I

Insert the IC socket into the PC board with the

notch in the direction shown on the top

legend. Solder the IC socket into place.

Insert the IC into the socket with the notch in

the same direction as the notch on the socket.

ASSEMBLE THE FOLLOWING COMPONENTS TO THE PC BOARD

In all of the following steps the components must be installed on the top legend side of the PC board. The

board is turned to solder the component leads on the foil side.

R13 - 18kW5% 1/4W Resistor

(brown-gray-orange-gold)

(see Figure A)

R14 - 100kW5% 1/4W Resistor

(brown-black-yellow-gold)

(see Figure A)

C3 - 1mF Electrolytic Radial

(see Figure G)

U5 - 8-pin IC Socket

U5 - 555 IC Timer

(see Figure I)

Notch

Marking

1. Connect the battery to the battery snap.

2. Set the voltmeter to read 20VAC and connect the

COM lead to the negative (–) side of the battery

and the V lead to pad of pin 8 of IC U3 as shown

in Figure 5. The meter should indicate 0V. Push

switch SW1. The meter should indicate 3-5VAC.

If not:

a) Check U5 and C3 to be sure that they are

installed as shown in the assembly

instructions.

b) Check R13 and R14 are the correct values.

Remove the battery from the battery snap and

the leads from the tester.

-9-

SECTION B - OSCILLATOR

The oscillator section consists of a 555 timing

circuit, resistors R13, R14, and capacitor C3. The

555 IC is configured as an astable or free-running

oscillator. The values of the resistor R14 and

capacitor C3 set the output frequency at 8Hz. The

IC will produce a continuous 8Hz square wave from

pin 3 as long as it is powered.

TESTING

Figure 4

To Switches

Figure 5

VCOM

VAC +

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