Polar Instruments T1000A User manual

Polar Instruments Ltd.
Garenne Park
St. Sampson
Guernsey
Channel Islands
GY2 4AF
ENGLAND
Fax: [phone]
MAN158–9604
T1000A
SERVICE
MANUAL

T1000A SERVICE 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. 1996

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

T1000A SERVICE MANUAL
ii
SAFETY
WARNING The service instructions contained in this manual
are for use by qualified electronic service personnel only.
WARNING
The LIVE and NEUTRAL lines on this unit are BOTH fused.
When the unit is connected to its supply, the opening of covers or removal of panels is
likely to expose dangerous voltages.
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
POWER SUPPLY
Check that the indicated line voltage setting corresponds with the local mains power
supply. See the rear panel for line voltage settings.

SAFETY
iii
Changing the line voltage settings on this instrument must only be performed by a
skilled electronics technician. Instructions for changing the line voltage settings are
contained in Section 4.
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 unit 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 instrument 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.
Static Sensitive Devices
This unit contains Static Sensitive Devices. Static discharge can damage some
electronic components. Care must be taken when handling these components. Observe
appropriate precautions to avoid damage.

T1000A SERVICE MANUAL
iv
SPECIFICATIONS
ASA Test Ranges Open Circuit Voltage Short Circuit Current
Junction 1V 500µA
Logic 10V 5mA
Low 10V 150mA
Med 20V 1mA
Hi-Cap (1Hz fixed) 10V 150mA
Low-Cap (2kHz fixed) 10V 20µA
ASA Test Frequencies
Low 95Hz
Medium 500Hz
High 2kHz
Curve Tracing
Collector drive Peak Voltage Peak Current
10V 10mA maximum
10V 100mA maximum
+/– selectable
Base Step Generator
Number of steps 8
Step amplitude 1V/step or 1mA/step (selectable)
Amplitude adjustable (0 – 100%)
Polarity (selectable)
Display Outputs to drive oscilloscope in X-Y mode
(100mV/div)
Power supply Detachable power cord

SPECIFICATIONS
v
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)
Power Requirements
230V ± 10%, 115V ± 10% or 100V ± 10% at 50/60Hz, 20VA.
Physical characteristics (excluding accessories)
Dimensions 300 mm (11.8 in.) wide
120 mm (4.7 in.) high
275 mm (10.8 in.) deep
Weight 2 kg (4.4 lb.)
Fuses
230V 80mAT
115V 160mAT
SYMBOLS
REFER TO MANUAL These sockets are for connecting only Polar Instruments
probes and connectors for use as described in the
Operator Manual. 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).

T1000A SERVICE MANUAL
vi
ACCESSORIES
Standard Accessories
Oscilloscope cable assembly ACC150
Probe set MMP159
Test clip set ACC110(Red)
ACC111(Black)
Operator manual MAN148

CONTENTS
vii
CONTENTS
DECLARATIONS..............................................................................................................i
ELECTROMAGNETIC COMPATIBILITY ......................................................................i
European Community Directive Conformance Statement..........................................i
SAFETY...........................................................................................................................ii
WARNING....................................................................................................................ii
GROUNDING ...............................................................................................................ii
POWER SUPPLY.........................................................................................................ii
OPERATION ...............................................................................................................iii
CAUTION ....................................................................................................................iii
Electrical Isolation.....................................................................................................iii
Static Sensitive Devices...........................................................................................iii
SPECIFICATIONS..........................................................................................................iv
ENVIRONMENTAL OPERATING CONDITIONS.........................................................v
Power Requirements.................................................................................................v
Physical characteristics (excluding accessories).......................................................v
Fuses.........................................................................................................................v
SYMBOLS ....................................................................................................................v
ACCESSORIES...........................................................................................................vi
Standard Accessories...............................................................................................vi
SECTION 1 – PERFORMANCE CHECK .................................................................... 1-1
MAINTENANCE AND CALIBRATION OF INSTRUMENTS ..................................... 1-1
Recommendations for Routine Maintenance ........................................................ 1-1
PERFORMANCE CHECK ........................................................................................ 1-1
Equipment required............................................................................................... 1-1
Procedure.............................................................................................................. 1-1
SECTION 2 – CIRCUIT DESCRIPTION...................................................................... 2-1
T1000A CIRCUIT DESCRIPTION............................................................................ 2-1
Sine Generator...................................................................................................... 2-1
SINE Amplifier and Power Supply......................................................................... 2-2
SINE amplifier................................................................................................. 2-2
Power Supply.................................................................................................. 2-2
Switching............................................................................................................... 2-2
Amplifier ................................................................................................................ 2-2
SECTION 3 – DISMANTLING INSTRUCTIONS ......................................................... 3-1
DISMANTLING THE T1000A ................................................................................... 3-1
Removing the cover............................................................................................... 3-1
Removing the circuit boards.................................................................................. 3-1

T1000A SERVICE MANUAL
viii
SECTION 4 – LINE VOLTAGE AND FUSE CHANGING............................................ 4-1
LINE VOLTAGE SELECTION AND FUSE CHANGING...........................................4-1
SECTION 5 – FAULT DIAGNOSIS ............................................................................. 5-1
TROUBLESHOOTING HINTS..................................................................................5-1
SECTION 6 – MAINTENANCE AND CLEANING........................................................ 6-1
Cleaning ................................................................................................................6-1
Technical Support..................................................................................................6-1
SECTION 7 – REPLACEMENT PARTS...................................................................... 7-1
ELECTRICAL PARTS............................................................................................... 7-2
MECHANICAL PARTS ............................................................................................. 7-5
SECTION 8 – SCHEMATIC DIAGRAMS..................................................................... 8-1

1-1
SECTION 1 – PERFORMANCE CHECK
MAINTENANCE AND CALIBRATION OF INSTRUMENTS
There are no calibration adjustments in this instrument.
Recommendations for Routine Maintenance
To ensure the functionality of the instrument it is recommended that its Performance
Check carried out at intervals not exceeding 12 months.
PERFORMANCE CHECK
The Performance Check is used to verify the functions of the instrument.
Equipment required
Oscilloscope
Procedure
1. Set the T1000A to LOGIC range, MED frequency.
Connect the oscilloscope ground to COM and set it for 5V/div. and 0.5mS/div.
Set the input to DC coupled and centre the trace.
Connect to A socket and trigger the oscilloscope.
Check for a sine wave of approximately 4 divisions pk to pk amplitude and 4
divisions period.
Connect to Channel B socket and confirm a similar display.
2. Set the T1000A to LOW range and check for a similar display from both sockets.
3. Set the T1000A to MED range
Check that the waveform at A and B is now approximately 8 divisions pk to pk
4. Set the oscilloscope to 0.1mS/div. and the T1000A to HIGH frequency.
Check for a period of sine wave of 5 divisions.
5. Set the T1000A to LOW frequency and the oscilloscope to 2mS/div.
Check for a period of approximately 4 divisions.
6. Set the T1000A to the JUNC range and MED frequency.
Set the oscilloscope to 0.5V/div. and 0.5mS/div.
Check for approximately 4 divisions pk to pk at the Channel A and B sockets.
7. Set the T1000A to 100mA drive in the CURVE TRACE mode. Set to + drive.
Set the oscilloscope to 5V/div.
Check for +ve going “rectified” sine wave of 2 divisions at Channel A or B socket
or “C” terminals of A or B test sockets.
8. Set the T1000A drive to – and 10mA.
Check for a –ve going 2 division waveform.

T1000A SERVICE MANUAL
1-2
9. Set the T1000A STEP AMPLITUDE to fully CW and + steps of Volts.
Check for a +ve going step waveform of about 1.5 divisions total amplitude.
10. Set the oscilloscope to XY mode and 0.1V/div. and connect the T1000A by its
oscilloscope cable (red to X).
Check each ASA range for two horizontal lines, adjusting A position if
necessary.
11. Select LOCAP and connect a 150pF capacitor between Channel B and COM.
Check for a near circular trace.
12. Select HICAP and connect a 2,200µF capacitor from Channel B to COM.
Check for the dot tracing out a near circular path (then a straight line and
repeat).
13. If a portable appliance tester is to be used, note that this product is earth
protected and that no exposed grounded parts exist on the enclosure.

2-1
SECTION 2 – CIRCUIT DESCRIPTION
T1000A CIRCUIT DESCRIPTION
Sine Generator
Refer to the T1000A Sine Generator schematic
Sine waves are generated by clocking a stored pattern out of Read Only Memory, ROM
U4, and into a Digital to Analog Converter, DAC U5. Frequency is changed by
switching clock rate.
U1A and B form the master clock oscillator controlled by 2MHz crystal X1. This clock is
divided down by U2 to provide the source frequencies for the synchronous ROM
address counter U3 and U8. 330R resistors are included to reduce RF emission. U203
acts as a 2 pole 4 way switch selecting one of the four source frequencies. This digital
switch is controlled by the front panel switch bank.
Nine address bits are used and in this system the MSB has the same frequency as the
sine wave. C9 is half this frequency, i.e. high for one cycle then low for the next. C10
(at half the frequency of C9) is high for two cycles then low for two. The Alternate
switching circuit, which allows two traces to be seen on the display, uses C9 or C10 as
the switching clock. The higher two frequencies (HIGH and MED) and very low
frequency for HICAP alternate every two cycles, the other (LOW) alternates every
cycle. Selection is via the second pole of switch U203.
ROM U4 stores the patterns for sine and +ve and –ve rectified sines in three different
areas of memory. Address bits A10 and A11 select the memory area scanned by the
counter. U5 converts the data to a current which op amp U6A converts into a voltage
sine wave. U5 pins 14 and 15 are a virtual earth and R20 sets the reference current for
the DAC.
The 5V pk sine wave is buffered by U6B and reduced to 1V pk by U6C. The capacitors
across the op amps provide phase correction to reduce looping of the trace. Extra
correction is applied in the JUNCTION range by analogue switch U200D.
The step waveform of the curve tracer base drive is generated from the digital address
count so that it is synchronised with the sine waves. Counts C7, C8 and C9 drive 5V
through weighted resistors R211, R12 and R13 into the summing input of op amp
U202D. The gain of this stage is controlled by the front panel step amplitude control
R11. Note that the AND gates are turned off in ASA to stop the step generator. The
output is inverted by U202A and drives the output through buffer U202B. Switch S9
(refer to T1000A Switching schematic) selects the polarity of the drive to the buffer.
SINE Amplifier and Power Supply
Refer to T1000A Power schematic

T1000A SERVICE MANUAL
2-2
SINE amplifier
The 5V sine wave is amplified to 10V pk for A and B outputs by U15 and U14 which are
power op-amps. Zener diodes clamp the outputs if a transient occurs while fuses F2
and F3 open to protect the op-amps if a sustained overload is applied.
The 20V pk for MED range is obtained from the bootstrapped op amp U16 which
amplifies the 5V to 20V. U17 amplifies the sine wave to 10V and couples this to the
power supply pins of U16 through C15 and C16. In this way the dynamic window of
about 25V of the op-amp is moved up and down to follow the sine wave. Diode D305
disconnects the +15V supply when C15 drives the +ve supply pin of the IC above
+15V. D306 operates similarly during –ve half cycles. C225 provides phase correction
unique to MED range.
Power Supply
The power supply is a simple conventional linear arrangement. The supplies for the
CMOS switches are zener regulated and current limited by the 3K3 series resistors
R49 and R50. This prevents latch up damage under fault conditions.
Switching
Refer to T1000A Switching schematic
Note: The schematic diagram is arranged to correspond exactly with the circuit board
layout as an aid to troubleshooting.
The mechanical switch bank is wired to interlock many of the T1000A functions. U200B
is a simple logic inverter of the control signal “JR”.
LEDs D16, D17 are both in the same dual colour package as are D18, D19 and D20,
D21.
Amplifier
Refer to the Amplifier schematic
The signals developed in the external node by the drive sine wave through the
appropriate series resistor are amplified by op-amps U9A and B and processed before
being fed to the display oscilloscope.
For Channel A (Channel B is identical) R43 is Riand R44 is Rffor the 10V ranges. R42
is switched across Rito lower the attenuation for the 1V JUNCTION range. Analogue
switch U200A places R202 in parallel with Rffor the MED range, halving the gain. All
ranges result in a 1V pk signal at output XA (or XB) when the terminals are open circuit.
In order to compute a current signal the X signal is combined with a reference sine
wave in op amp U9C. C207 rolls off the response to RF (as does C206 at the input
amp) and C222 provides further phase correction. C221 is added in parallel in the
LOCAP range.

CIRCUIT DESCRIPTION
2-3
CMOS changeover switch U10 is located in the virtual earth of the output op amps. It
switches between channels at a rate dependant on the ALT_CLK signal, which is once
per cycle of sine wave or every two cycles depending on range. Position offset is added
to the A signal at this point.
The outputs are scaled to drive 10 divisions horizontally and 8 divisions vertically at
0.1V/div. on the display oscilloscope.

3-1
SECTION 3 – DISMANTLING INSTRUCTIONS
DISMANTLING THE T1000A
Removing the cover
•Disconnect the power cord.
•To remove the cover, undo the two screws at the rear and lift the rear
of the cover first.
Removing the circuit boards
•Unsolder the wires from the A, COM and B sockets.
•Remove the two nuts and bolts from the power inlet.
•Remove the two screws holding the position control PCB and swing
this out.
•Remove the screws holding the boards to the case.
•Remove the power button cap by pulling off.
•Holding the power switch shaft in lift the rear of the main board
withdraw the circuit boards assembly from the case.
•Re-assembly is the reverse of the above.

4-1
SECTION 4 – LINE VOLTAGE AND FUSE CHANGING
WARNING: There are hazardous voltages inside the instrument when
connected to its power supply. REMOVE THE POWER CORD before
touching any part of the line input circuit. Note that high voltages may
continue to be present for 2 minutes after power is removed until internal
capacitors discharge.
LINE VOLTAGE SELECTION AND FUSE CHANGING
Note: When replacing fuses always use the type and rating stated in SPECIFICATIONS.
To change the line voltage, pull out the links from their sockets using suitable pliers and
place them in the locations marked with the required voltage. Install the fuse(s) of the
value indicated in SPECIFICATIONS.

5-1
SECTION 5 – FAULT DIAGNOSIS
WARNING: Hazardous voltages are exposed on the PCB when the cover
is removed. These procedures should only be performed by a technically
qualified person aware of the hazards and taking all reasonable care.
TROUBLESHOOTING HINTS
•If no LEDs light up check the mains fuse. (Note that Neutral is also
fused in some countries). Check the line voltage selector and look for
any evidence of component failure.
•Once the unit is working confirm the presence of all voltages at the
test pads on the main PCB. Note that VEE is –5V and VDD is +5V for
the CMOS switches. If these are loaded down look for wrong voltage
levels around the switches.
•Start circuit checks at the sine wave generator. If no sine wave
appears to be present check the crystal oscillator is running.
•A possible problem area is the 10V drive amplifier. Check the output
fuses are intact first. Check that the protection devices have not been
overloaded or any series resistors damaged.
•Find out what is working and what is not. Read the description of each
circuit block and try to identify which part of the circuit is not working
then investigate this.

6-1
SECTION 6 – MAINTENANCE AND CLEANING
Cleaning
Disconnect the instruments power cord.
Clean the unit with a cloth lightly moistened with water with a small amount of mild
detergent.
Alternatively, a cloth lightly moistened with alcohol (ethanol or methylated spirit) or
Iso-propyl alcohol (IPA) may be used (Caution — these are inflammable).
Do not spray cleaners directly onto the instrument.
Do not reconnect the power until dry.
Technical Support
For technical support contact your local Polar Instruments distributor or Polar
Instruments Ltd. at the address at the front of this manual.
Instrument repair
If it becomes necessary to repair the instrument, in the first instance contact the
Polar Instruments distributor in your country. In case of difficulty contact Polar
Instruments Ltd. at the address at the front of this manual. Do not send the
instrument until shipping instructions have been received from the repairer.