Polar Instruments T1500A User manual

Polar Instruments Ltd.
Garenne Park
Rue de la Cache
St. Sampson
Guernsey
Channel Islands
GY2 4AF
England
Fax: [phone]
MAN 151-9510
T1500A
OPERATOR
MANUAL

T1500A FAULT LOCATOR OPERATOR MANUAL
WARRANTY
For a period of one year from its date of purchase new and undamaged from Polar
Instruments Ltd, POLAR INSTRUMENTS LTD or its authorized distributors will, without
charge, repair or replace at its option, this product if found to be defective in materials
or workmanship, and if returned to POLAR INSTRUMENTS LTD or its authorized
distributors transport prepaid. This warranty is expressly conditioned upon the product
having been used only in normal usage and service in accordance with instructions of
POLAR INSTRUMENTS LTD and not having been altered in any way or subject to
misuse, negligence or damage, and not having been repaired or attempted to be
repaired by any other than POLAR INSTRUMENTS LTD or its authorized distributors.
EXCEPT FOR THE FOREGOING EXPRESS WARRANTY OF REPAIR OR
REPLACEMENT POLAR INSTRUMENTS LTD MAKES NO WARRANTY OF ANY
KIND, INCLUDING BUT NOT LIMITED TO, ANY EXPRESS OR IMPLIED WARRANTY
OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE, AND
POLAR INSTRUMENTS LTD SHALL NOT BE LIABLE FOR ANY DAMAGES,
WHETHER DIRECT OR NOT OR OTHERWISE, BEYOND REPAIR OR REPLACING
THIS PRODUCT.
Copyright Polar Instruments Ltd. 1995

T1500A OPERATOR MANUAL
ii
DECLARATIONS
ELECTROMAGNETIC COMPATIBILITY
European Community Directive Conformance Statement
This product is in conformity with the protection requirements of EC Council Directive
89/336/EEC on the approximation of the laws of the Member States relating to
electromagnetic compatibility.
A declaration of conformity with the requirements of the Directive has been signed by
POLAR INSTRUMENTS (UK) LTD
11 College Place
London Road
Southampton
England
SO1 2FE
This product satisfies EN50081-1:92 and EN 50082-1:92

SAFETY
iii
SAFETY
WARNING
The LIVE and NEUTRAL lines on this unit are BOTH fused.
This unit contains no user-serviceable parts. When the unit is connected to its supply,
the opening of covers or removal of panels is likely to expose dangerous voltages. To
maintain operator safety, do not operate the unit unless the enclosure is complete and
securely assembled.
GROUNDING
This unit must be earthed (grounded); do not operate the instrument with the safety
earth disconnected. Ensure the instrument is connected to an outlet with an effective
protective conductor terminal (earth). Do not negate this protective action by using an
extension cord without a protective conductor.
Note: This instrument is fitted with 3-wire grounding type plug designed to fit only into a
grounding type power outlet. If a special local plug must be fitted to the power cord
ensure this operation is performed by a skilled electronics technician and that the
protective ground connection is maintained. The plug that is cut off from the power cord
must be safely disposed of.
Power cord color codes are as follows:
Europe
brown live
blue neutral
green/yellow earth (ground)
United States
black live
white neutral
green ground

T1500A OPERATOR MANUAL
iv
POWER SUPPLY
Check that the indicated line voltage setting corresponds with the local mains power
supply. See the rear panel for line voltage settings.
To change the line voltage settings refer the instrument to a skilled electronics
technician. Instructions for changing the line voltage settings are contained in the
T1500A Service Manual published by Polar Instruments.
T1500A OPERATION
This manual contains instructions and warnings which must be observed
by the user to ensure safe operation. Operating this instrument in ways
other than detailed in this manual may impair the protection provided by
the instrument and may result in the instrument becoming unsafe. Retain
these instructions for later use.
The T1500A is designed for use indoors in an electrical workshop environment at a
stable work station comprising a bench or similar work surface.
Use only the accessories (e.g. test probes and clips) provided by Polar Instruments.
The T1500A must be maintained and repaired by a skilled electronics technician in
accordance with the manufacturer’s instructions.
If it is likely that the protection has been impaired the instrument must be made
inoperative, secured against unintended operation and referred to qualified service
personnel. Protection may be impaired if, for example, the instrument:
•Shows signs of physical damage
•Fails to operate normally when the operating instructions are followed
•Has been stored for prolonged periods under unfavourable conditions
•Has been subjected to excessive transport stresses
•Has been exposed to rain or water or been subject to liquid spills
CAUTION
Electrical Isolation
Always disconnect the board under test from the local mains supply (including ground)
before using this instrument. SPECIFICATIONS

SPECIFICATIONS
v
ASA Test Ranges Open Circuit Voltage Short Circuit Current
Junction 1V 500µA
Logic 10V 5mA
Low 10V 150mA
Med 20V 1mA
High 40V 1mA
Hi-Cap (1Hz fixed) 10V 150mA
Low-Cap (2kHz fixed) 10V 20µA
ASA Test Frequencies
Low 95Hz
Medium 500Hz
High 2kHz
Display Internal CRT
Power Requirements
230V ± 10%, 115V ± 10% or 100V ± 10% at 50/60Hz, 40VA.
Physical characteristics (excluding accessories)
Dimensions 300 mm (11.8 in.) wide
110 mm (4.4 in.) high
260 mm (10.3 in.) deep
Weight 1.5 kg (3.3 lb.)
ENVIRONMENTAL OPERATING CONDITIONS
The instrument is designed for indoor use only under the following environmental
conditions:
Altitude Up to 2000m
Temperature +5°C to +40°C ambient
Relative humidity RH 80% maximum at 31°C — derate
linearly to 50% at 40°C
Mains borne transients As defined by Installation Category II
(Overvoltage Category II) in IEC664
Pollution Degree 2 (IEC664)

T1500A OPERATOR MANUAL
vi
ACCESSORIES
Standard Accessories
Probe set MMP159
Test clip set ACC110 (Red)
ACC111 (Black)
Operator manual MAN151
SYMBOLS
CAUTION To prevent damage to this product and to ensure its safe use
observe the specifications given in this manual when connecting to
terminals marked with this symbol.
COM This terminal is internally connected to earth (ground).

SPECIFICATIONS
vii
GUIDE TO THE MANUAL
INTRODUCTION An overview of the Polar T1500A fault locator
and its applications.
GENERAL DESCRIPTION A description of the principles of operation and
front and rear panels.
INSTALLATION AND SET UP Connecting the T1500A to a power supply.
ASA DEVICE TESTING Information about the different ways in which
the ASA facilities of the T1500A can be used
and how to test devices.
ASA SEMICONDUCTOR TESTING Describes methods of testing signal diodes,
zener diodes, LEDs and transistors in circuit.
SIMPLE MAINTENANCE Details of maintenance and cleaning
procedures.

T1500A OPERATOR MANUAL
viii
CONTENTS
DECLARATIONS........................................................................................................ii
ELECTROMAGNETIC COMPATIBILITY......................................................................ii
European Community Directive Conformance Statement....................................ii
SAFETY.....................................................................................................................iii
WARNING...................................................................................................................iii
GROUNDING ..............................................................................................................iii
POWER SUPPLY........................................................................................................iv
T1500A OPERATION..................................................................................................iv
CAUTION.....................................................................................................................iv
Electrical Isolation.........................................................................................iv
SPECIFICATIONS.....................................................................................................iv
ENVIRONMENTAL OPERATING CONDITIONS .........................................................v
ACCESSORIES...........................................................................................................vi
Standard Accessories..........................................................................................vi
SYMBOLS ...................................................................................................................vi
SECTION 1 – INTRODUCTION.............................................................................. 1-1
THE T1500A FAULT LOCATOR.............................................................................. 1-1
1-1 Introduction to the T1500A......................................................................... 1-1
1-2 Areas of application.................................................................................... 1-1
1-3 Analog Signature Analysis..........................................................................1-1
SECTION 2 – GENERAL DESCRIPTION.............................................................. 2-1
PRINCIPLES OF OPERATION ................................................................................ 2-1
2-1 T1500A controls, connectors and probes................................................... 2-1
The T1500A front panel............................................................................. 2-1
The T1500A rear panel.............................................................................. 2-1
2-2 Producing signatures.................................................................................. 2-1
2-3 Four-quadrant signatures........................................................................... 2-2
2-4 The T1500A equivalent circuit.................................................................... 2-3
SECTION 3 – INSTALLATION AND SET-UP ........................................................ 3-1
PREPARATION FOR USE....................................................................................... 3-1
3-1 Unpacking .................................................................................................. 3-1
3-2 Connecting the T1500A to a power supply................................................. 3-1
3-3 Setting up the T1500A................................................................................ 3-2
3-4 Connecting the test cables......................................................................... 3-3
Single Channel Applications ...................................................................... 3-3
Dual Channel (Comparison) Applications.................................................. 3-3

CONTENTS
ix
SECTION 4 – ASA DEVICE TESTING................................................................... 4-1
TESTING COMPONENTS ....................................................................................... 4-1
4-1 ASA techniques.......................................................................................... 4-2
Troubleshooting without documentation .................................................... 4-2
Typical faults.............................................................................................. 4-3
4-2 Testing resistors......................................................................................... 4-4
4-3 Testing capacitors...................................................................................... 4-6
Choosing capacitor testing ranges............................................................. 4-7
Leakage current in capacitors.................................................................... 4-8
Capacitors in circuit.................................................................................... 4-9
4-4 Inductors .................................................................................................. 4-10
Signatures of inductors............................................................................ 4-10
SECTION 5 – ASA SEMICONDUCTOR TESTING ................................................ 5-1
USING ASA TO TEST SEMICONDUCTORS........................................................... 5-1
5-1 Diodes, LEDs and Zeners.......................................................................... 5-1
5-2 Testing transistors in circuit........................................................................ 5-3
Identifying Transistor Terminals................................................................. 5-3
5-3 Field Effect Transistors (FETs)................................................................... 5-5
Junction FETs (JFETs) .............................................................................. 5-5
Metal-Oxide Semiconductor FETs (MOSFETs)......................................... 5-5
5-4 Integrated Circuits...................................................................................... 5-5
5-5 Testing Devices in Circuit......................................................................... 5-10
Circuit Example........................................................................................ 5-10
5-6 Testing Bus-connected devices ............................................................... 5-13
SECTION 6 – SIMPLE MAINTENANCE AND CLEANING .................................... 6-1
Fault diagnosis ................................................................................................. 6-1
Cleaning........................................................................................................... 6-1
Technical Support ............................................................................................ 6-1

1-1
SECTION 1 – INTRODUCTION
THE T1500A FAULT LOCATOR
1-1 Introduction to the T1500A
The T1500A Fault Locator provides a fast and efficient means of testing
components, either in isolation or in circuit.
All testing is done with power disconnected from the circuit, so there is no risk to the
user and components under test cannot be damaged.
Two channels, A and B, enable the characteristics of a reference and a faulty
component or circuit to be compared. Faults in complex circuits can thus be
diagnosed without a high degree of technical skill or detailed knowledge of the circuit
functions — this facility will be found particularly useful when documentation is not
available.
1-2 Areas of application
The T1500A is an ideal instrument for a wide range of applications:
•Field Service – fault finding.
•Manufacturing – goods inwards testing and troubleshooting.
•Repair – rapid diagnostics.
•Education – examination of device characteristics.
1-3 Analog Signature Analysis
The T1500A Fault Locator tests components by applying a current-limited alternating
(AC) drive voltage across the component and monitoring the resultant current flow to
display impedance signatures. Signatures for different types of components have
distinctly different shapes that can be easily distinguished.
The inclusion of two channels in the T1500A allows the user to compare the
behaviour of two devices simultaneously.

2-1
SECTION 2 – GENERAL DESCRIPTION
PRINCIPLES OF OPERATION
2-1 T1500A controls, connectors and probes
The T1500A front panel
The front panel comprises:
Display Intensity — use to adjust display brightness
Trace Rotation — use to control trace orientation.
ASA range and frequency switches — use the voltage range and frequency switches to
select appropriate drive voltages and frequencies during signature analysis.
Channel A and B probes — probe across devices (between Channel A and COM or
Channel B and COM) to observe device signatures.
COM (common return) connector — connect the COM test clip to the ground of the
board (or boards) under test.
Channel A position controls — use the Channel A position controls to move the
channel A trace vertically and horizontally with respect to the Channel B trace.
The T1500A rear panel
The IEC power connector and power ON/OFF switch are mounted on the rear of the
instrument.
2-2 Producing signatures
The T1500A applies an alternating voltage to a component or circuit and displays the
resulting current versus voltage display on a CRT screen.
The voltage applied across the component is displayed horizontally, the current through
the component is displayed vertically, so the resulting V/I graph represents the
resistance, or impedance, of the component. This is defined as the Impedance
Signature of the device.
The T1500A generates voltages of both polarities, i.e. applies both positive and
negative voltages to a component, causing current to flow in both directions. The result
is a four quadrant graph (see Figure 2-1).

T1500A OPERATOR MANUAL
2-2
Figure 2-1 The T1500A CRT Display
2-3 Four-quadrant signatures
Impedance signatures are graphs of current against voltage, plotted on a scale which
has its origin at the centre of the CRT display screen.
As the voltage applied to the component is driven positive and negative, positive
voltages and currents are displayed in the upper right quadrant on the CRT, negative
voltages and currents are displayed in the lower left quadrant.
The graticule marked on the CRT face is graduated so approximate current and
voltage measurements can be made.
It is usually not necessary, however, to calculate actual current values in a component
to verify its correct operation. When fault finding on an electrical circuit, the technician
is frequently looking for components that have failed completely. Often, a brief glance
at the signature of a suspect device will be sufficient to show whether it is good or
defective.
1st Quadrant2nd Quadrant
3rd Quadrant 4th Quadrant
+V
+I
-V
-I
Horizontal (Voltage) Axis
Vertical (Current) Axis

GENERAL DESCRIPTION
2-3
2-4 The T1500A equivalent circuit
The T1500A can be represented by a voltage source, VS, in series with an internal (or
source) impedance, ZS, and the component under test by a simple impedance, ZL
(Figure 2-2).
Figure 2-2 T1500A equivalent circuit
The T1500A contains circuits which measure the voltage across, and the current
through, the component to be tested and output a display on the CRT.
The voltage, VL, across the impedance, ZL, will depend on the impedance of the
component under test and controls the horizontal deflection of the display.
Current through the component under test will cause a voltage to be developed across
the T1500A internal impedance, ZS. This voltage controls the amount of vertical
deflection on the display.
A high value impedance in the component under test (that is, high compared with the
value of ZS)will result in low circuit current (and therefore a low voltage across ZS)with
most of the T1500A source voltage, VS,appearing across ZL, producing a signature
with a shallow slope.
A low value impedance will result in high circuit current and most of the source voltage
developed across ZS; the result is a steeply sloping signature.
Vs
Zs
ZL
A
VL

T1500A OPERATOR MANUAL
2-4
Figure 2-3 shows the signatures of two resistors, measured on the same voltage range,
superimposed. Component B has a greater resistance then component A.
Figure 2-3 T1500A display showing two impedance signatures
AB

3-1
SECTION 3 – INSTALLATION AND SET-UP
PREPARATION FOR USE
3-1 Unpacking
The instrument is shipped in a sturdy transit pack. Open the pack carefully and remove
the instrument and its accessories.
If the instrument is damaged in any way contact the local distributor or supplier.
Retain the pack for possible future use.
The T1500A pack should contain:
T1500A
Power cord
Pair of probes
Pair of test clips
Operator manual
Note: If the instrument has been shipped or stored in a cold environment, allow the
instrument to reach the temperature of its new location before applying power.
3-2 Connecting the T1500A to a power supply
Refer to the voltage label on the rear panel of the instrument and make sure that
the marked rating is suitable for the local mains power supply.
If the rating on the label is not suitable for the local power supply refer the instrument to
a skilled electronics technician. Instructions for changing the line voltage settings are
contained in the T1500A Service Manual.
Note: If a special local plug must be fitted to the power cord ensure this operation is
performed by a skilled electronics technician and that the protective ground connection
is maintained. The plug that is cut off from the power cord must be safely disposed of.

T1500A OPERATOR MANUAL
3-2
Power cord color codes are as follows:
Europe
brown live
blue neutral
green/yellow earth (ground)
United States
black live
white neutral
green ground
3-3 Setting up the T1500A
1. Connect the power cord to the T1500A and to the power supply and
switch on (the power switch is located at the rear of the instrument).
The screen should display the Channel A and B outputs (two horizontal
traces) about the screen centre.
Caution: The CRT phosphor could be burnt if the intensity is set too high
and the same display is left on the screen for several hours.
Rotate the A POSITION horizontal and vertical controls and ensure that
the Channel A trace moves correctly vertically and horizontally with
respect to the Channel B trace. Adjust the X and Y position controls to
centre the traces about the screen centre.
2. If the CRT trace is not perfectly horizontal, adjust the Trace Rotation
control until the trace is parallel to the X axis. If the instrument is moved
to a new location readjustment of the Trace Rotation control may be
necessary.
3. Select the LOGIC RANGE and LOW FREQUENCY.

INSTALLATION AND SET-UP
3-3
3-4 Connecting the test cables
Single Channel Applications
With the Red probe connected to the Channel A (or Channel B) socket, and the Black
probe to the COM socket connect the probes across the device. When checking a
signature at a node in a circuit it will often be appropriate to connect the COM socket to
a convenient ground point using either a probe or test clip.
Dual Channel (Comparison) Applications
Connect the Red probe to the Channel A socket, the Black probe to the Channel B
socket, and a test clip to the COM socket. Connect the COM test clip to the ground of
the board under test.
If two boards are being compared, both grounds must be connected to the instrument's
COM sockets.

4-1
SECTION 4 – ASA DEVICE TESTING
TESTING COMPONENTS
Using the Analog Signature Analysis method, safe, low power drive voltages are
applied to components to produce "impedance signatures" on the oscilloscope screen.
Impedance signatures are graphs of current against voltage, plotted on a scale which
has its origin at the centre of the screen. This may be carried out on devices in or out of
circuit. Positive voltages and currents are displayed in the upper right quadrant on the
display. Negative voltages and currents are displayed in the lower left quadrant (see
Figure 4-1 Display X and Y Axis).
Figure 4-1 Display X and Y Axis
The graticule marks on the CRT face can be used for actual current and voltage
measurements. Table 4-1 shows the scales for each voltage range.
Range Peak Voltage Horizontal Peak
Current Vertical
Junction 1V 0.2V/div 500µA 0.125mA/div
Logic 10V 2V/div 5mA 1.25mA/div
Low 10V 2V/div 150mA 37.5mA/div
Med 20V 4V/div 1mA 0.25mA/div
High 50V 10V/div 1mA 0.25mA/div
Hi-Cap 10V 2V/div 150mA 37.5mA/div
Lo-Cap 10V 2V/div 20µA5µA/div.
Table 4-1 Drive Ranges