Elenco DataCom Tester Kit User Manual

MULTI-NETWORK CABLE TESTER KIT

MODEL TCT-255K

Copyright © 2013, 2001 by ELENCO®All rights reserved. REV-D 753089

No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

ELENCO

®

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 Termina tor LD-10 0

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 RJ­45 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

-2-

Warning:

If the capacitor is
connected with
incorrect polarity, it
may heat up and
either leak, or
cause the capacitor
to explode.

IDENTIFYING RESISTOR VALUES

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

BANDS

METRIC UNITS AND CONVERSIONS

Abbreviation Means Multiply Unit By Or

p Pico .000000000001 10

-12

n nano .000000001 10

-9

µ micro .000001 10

-6

m milli .001 10

-3

– unit 1 10

0

k kilo 1,000 10

3

M mega 1,000,000 10

6

1. 1,000 pico units = 1 nano unit

2. 1,000 nano units = 1 micro unit

3. 1,000 micro units = 1 milli unit

4. 1,000 milli units = 1 unit

5. 1,000 units = 1 kilo unit

6. 1,000 kilo units = 1 mega unit

IDENTIFYING CAPACITOR VALUES

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

Electrolytic capacitors have a positive
and a negative electrode. The
negative lead is indicated on the
packaging by a stripe with minus
signs and possibly arrowheads. Also,
the negative lead of a radial
electrolytic is shorter than the positive
one.

Polarity
marking

BAND 1

1st Digit

Color Digit

Black 0
Brown

1

Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Gray 8
White 9

BAND 2

2nd Digit

Color Digit

Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Gray 8
White 9

Multiplier

Color Multiplier

Black 1
Brown 10
Red 100
Orange 1,000
Yellow 10,000
Green 100,000
Blue 1,000,000
Silver 0.01
Gold 0.1

Resistance

Tole rance

Color Tol eran ce

Silver ±10%
Gold ±5%
Brown ±1%
Red ±2%
Orange ±3%
Green ±0.5%
Blue ±0.25%
Violet ±0.1%

1

2 Multiplier Tolerance

Multiplier

For the No. 0 1 2 3 4 5 8 9

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

(+)

(–)

(+)

(–)

Axial

Radial

Second digit

First digit

Multiplier

Tolerance*

Note: The letter “R” may be used at times
to signify a decimal point; as in 3R3 = 3.3

The letter M indicates a tolerance of +20%
The letter K indicates a tolerance of +10%
The letter J indicates a tolerance of +5%

Maximum working voltage

(may or may not appear
on the cap)

The value is 10 x 10 =
100pF, +10%, 50V

*

CERAMIC DISC MYLAR

First digit

Second digit

Multiplier

Tolerance*

2A222J

100V

The value is 22 x 100 =
2,200pF or .0022µF, +5%, 100V

101K

50V

-3-

CONSTRUCTION

Introduction

The most important factor in assembling your TCT-255 Multi-Netwok 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.

Solder

For many years leaded solder was the most common type of solder used by the electronics
industry, but it is now being replaced by lead-free solder for health reasons. This kit contains
lead-free solder, which contains 99.3% tin, 0.7% copper, and has a rosin-flux core.

Lead-free solder is different from lead solder: It has a higher melting point than lead solder, so
you need higher temperature for the solder to flow properly. Recommended tip temperature is
approximately 700OF; higher temperatures improve solder flow but accelerate tip decay. An
increase in soldering time may be required to achieve good results. Soldering iron tips wear
out faster since lead-free solders are more corrosive and the higher soldering temperatures
accelerate corrosion, so proper tip care is important. The solder joint finish will look slightly
duller with lead-free solders.

Use these procedures to increase the life of your soldering iron tip when using lead-free
solder:

• Keep the iron tinned at all times.

• Use the correct tip size for best heat transfer. The conical tip is the most commonly used.

• Turn off iron when not in use or reduce temperature setting when using a soldering station.

•

Tips should be cleaned frequently to remove oxidation before it becomes impossible to remove.
Use Dry Tip Cleaner (Elenco®#SH-1025) or Tip Cleaner (Elenco®#TTC1). If you use a sponge to
clean your tip, then use distilled water (tap water has impurities that accelerate corrosion).

Safety Procedures

• Always wear safety glasses or safety goggles to protect your eyes when
working with tools or soldering iron, and during all phases of testing.

• Be sure there is adequate ventilation when soldering.

•

Locate soldering iron in an area where you do not have to go around it or reach over it. Keep
it in a safe area away from the reach of children.

• Do not hold solder in your mouth. Solder is a toxic substance. Wash hands thoroughly
after handling solder.

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 in the board and are soldered on the foil side.

Use only rosin core solder.

DO NOT USE ACID CORE SOLDER!

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.

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-

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.

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.

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

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.

1. Insufficient heat - the solder will

not flow onto the lead as shown.

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.

4.

Here is what a good solder
connection looks like.

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.

What Good Soldering Looks Like

A good solder connection should be bright, shiny, smooth, and uniformly
flowed over all surfaces.

Types of Poor Soldering Connections

PARTS LIST - SECTION A

RESISTORS

Qty. Symbol Description Color Code Part #

! 2 R12, R17 1kΩ 5% 1/4W brown-black-red-gold 141000
! 1 R16 5.6kΩ 5% 1/4W green-blue-red-gold 145600
! 1 R15 12kΩ 5% 1/4W brown-red-orange-gold 151200
! 1 R9 3.3MΩ 5% 1/4W orange-orange-green-gold 173300

CAPACITORS

Qty. Symbol Value Description Part #

! 1 C2 22µF 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 Tube, Lead-free 9LF99

* 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

Tubi ng

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 - 1kΩ 5% 1/4W Resistor

(brown-black-red-gold)

(see Figure A)

D19 - LED Red
Tubing
Spacer

(see Figure B)

R9 - 3.3MΩ 5% 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 - 5.6kΩ 5% 1/4W Resistor

(green-blue-red-gold)

(see Figure A)

C2 - 22µF Electrolytic

(see Figure G)

R15 - 12kΩ 5% 1/4W Resistor

(brown-red-orange-gold)

(see Figure A)

R12 - 1kΩ 5% 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.

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

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”

Warning:

If the capacitor is connected
with incorrect polarity, it may
heat up and either leak, or
cause the capacitor to
explode.

Polarity Marking

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.

! 3. 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.

P

ush 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”

V

COM

VDC

+

9V

Figure 2

1

8

PARTS LIST - SECTION B

RESISTORS

Qty. Symbol Description Color Code Part #

! 1 R13 18kΩ 5% 1/4W brown-gray-orange-gold 151800
! 1 R14 100kΩ 5% 1/4W brown-black-yellow-gold 161000

CAPACITORS

Qty. Symbol Value Description Part #

! 1 C3 1µF 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 - 18kΩ 5% 1/4W Resistor

(brown-gray-orange-gold)

(see Figure A)

R14 - 100kΩ 5% 1/4W Resistor

(brown-black-yellow-gold)

(see Figure A)

C3 - 1µF Electrolytic Radial

(see Figure G)

U5 - 8-pin IC Socket
U5 - 555 IC Timer

(see Figure I)

Notch

Notch

Marking