Picotest M3500A User manual

PICOTEST®
M3500A
6.5 Digit Digital Multimeter
Service Manual
Printed date: 11/2011

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Table of Contents
1GENERAL INFORMATION.......................................................................................4
1.1 WARRANTY INFORMATION................................................................................4
1.2 LIMITATION OF WARRANTY ..............................................................................5
1.3 PRECAUTION OF OPERATION ............................................................................5
1.4 MAINTENANCE OF M3500A.............................................................................6
1.5 SAFETY INFORMATION ......................................................................................6
1.6 SYMBOLS AND TERMS.......................................................................................7
2GENERAL MAINTENANCE .......................................................................................8
2.1 SETTING LINE VOLTAGE AND REPLACING FUSE..............................................8
2.1.1 Voltage Selector.................................................................................8
2.1.2 Transformer.......................................................................................11
2.1.3 Power Line Fuse................................................................................13
2.2 CURRENT INPUT FUSE –3.15 A...................................................................15
2.2.1 Current Input Fuse – 7 A...................................................................18
2.3 PASS/FAIL OUTPUT FROM USB CONNECTOR ...............................................21
2.4 MCUS &DSP FIRMWARE UPGRADE .............................................................22
3TROUBLESHOOTING...............................................................................................26
3.1 INTRODUCTION ...............................................................................................26
3.2 SYSTEM FUNCTION BLOCKS...........................................................................28
3.3 PANEL MODULE...............................................................................................29
3.4 MAIN BOARD MODULE....................................................................................30
3.4.1 Power Supply Circuitry...................................................................31
3.4.2 Analog Front-end Circuitry............................................................32
3.4.3 ADC & MCU.........................................................................................33
3.4.4 Main Control Circuitry.....................................................................34
3.5 SELF-TEST.......................................................................................................35
4DISASSEMBLY & RE-ASSEMBLY.......................................................................39
4.1 INTRODUCTION ...............................................................................................39
4.2 CASE COVER REMOVAL ..................................................................................39
4.3 MAIN BOARD REMOVAL..................................................................................42
4.4 FRONT PANEL DISASSEMBLY..........................................................................48
4.5 ASSEMBLY DRAWINGS....................................................................................51
4.5.1 Front Panel Assembly .....................................................................52
4.5.2 Chassis and Transformer Assembly...........................................53

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4.5.3 Main Board Assembly......................................................................54
4.5.4 Chassis Assembly.............................................................................56
4.5.5 GPIB Assembly..................................................................................58
5REPLACEABLE PARTS.............................................................................................61
5.1 INTRODUCTION ...............................................................................................61
5.2 PARTS LIST .....................................................................................................61
5.3 LAYOUT DRAWINGS ........................................................................................82
6SIMPLE CALIBRATION PROCEDURES ....................................................................85
6.1 THE CALIBRATION SECURITY CODE...............................................................85
6.2 THE ZERO ADJUSTMENT.................................................................................85
6.3 THE GAIN ADJUSTMENT FOR DCV,DCI,4W&FREQ ...............................................86
6.4 THE GAIN ADJUSTMENT FOR ACV ...........................................................................87
6.5 CALIBRATION COUNT ............................................................................................88
6.6 CALIBRATION DATE ..............................................................................................88
6.7 THE CALIBRATION ERROR MESSAGES ...........................................................88
APPENDIX.............................................................................................................................89
A. SPECIFICATION LIST.......................................................................................89
B. GENERAL SPECIFICATIONS.............................................................................92

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1General Information
1.1 Warranty Information
Warranty: PICOTEST CORP. guarantees that this product meets its
published specifications at the time of shipment from the factory. Under
proper installation it should work as expected.
Warranty Period: This equipment is warranted against defects in
material and manufacturing for a period of one year from the date of
shipment. During the warranty period, PICOTEST is responsible for
necessary repairs as long as the product can be proved to be defective.
For warranty service or repair this product must be returned to a service
facility designated by PICOTEST. Please contact your local service
representative.
Excluded Items: This warranty does not include consumptive parts
such as fuses, buttons and relays. Neither does this warranty cover
defects caused by improper installation, improper or insufficient
maintenance, unauthorized modification, and improper operation,
ignorance of environmental specifications or improper software or
interfacing.
Remarks:
1. No other warranty is expressed or implied, except for the above
mentioned.
2. The remedies provided herein are the buyer’s sole and exclusive
remedies. PICOTEST shall not be liable for any direct, indirect,
special, incidental or consequential damages.

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1.2 Limitation of Warranty
Our warranties do not cover any damage resulting from unauthorized
modification or misuse.
Unless mentioned elsewhere in this document, our warranty does not
apply to fuses, probes, and problems arising from normal wear or user’s
failure to follow instructions.
Our warranties do not apply on any direct, incidental, special, or
consequential damages.
The above warranties are exclusive and no other warranty is
expressed or implied. PICOTEST disclaims any implied warranties of
MERCHANTABILITY, SATISFACTORY QUALITY, and FITNESS for any
particular reasons.
1.3 Precaution of Operation
Please carefully read the manual before operating this device.
This manual is for reference only. Please consult your local service
representative for further assistance.
The contents of this manual may be amended by the manufacturer
without notice.
Never dismantle the equipment by any unauthorized personnel, or
equipment may be damaged.
The equipment has been strictly tested for quality before delivery from
our factory. However, this equipment must not be used in dangerous
situations or damage may result.
This product should be placed in a safe area in case of unpredictable
personnel use.
The rear protective conduct terminal needs to be connected to the actual
earth ground or electric shock may occur.
The patent and related documents for the equipment belong to
PICOTEST CORP. and they aren’t allowed to be used by others without
permission.

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1.4 Maintenance of M3500A
Although M3500A multimeter is very durable and weather resistant, care
should be taken not to expose it to severe impact or pressure.
Keep M3500A far from water and damp environment.
Calibration should be taken every year. Please contact with your local
service representative for more information.
If the incorrect display or abnormal beeps occurred you should stop using
the equipment at once.
Do not use the Meter around explosive gas or inflammable vapor.
Wipe the surface of M3500A multimeter with a piece of dry and clean
cloth.
1.5 Safety Information
Warning! Please read through the following safety information before
using the product.
To avoid possible electric shock or personal injury, please read and follow
these guidelines carefully:
Follow the guidelines in this manual and DO NOT use the Meter if the case
is damaged. Check the Meter case and terminals, and make sure all the
devices are in the proper positions.
Do not apply excessive voltage to the Multimeter. Apply voltage within
the rated range only.
Use caution when measuring voltages above 30 V RMS, 42 V peak, or 60
V DC. These voltages pose an electric shock hazard.
When using the probes, always keep your fingers behind the finger
guards.
Always connect the common test leads (black) before connecting the live
test leads (red), and disconnect the live test leads (red) before
disconnecting the common test leads (black). This will reduce the chance
of an electric shock.

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Disconnect circuit power and discharge all high-voltage capacitors before
testing resistance, continuity, diodes or capacitance.
If you need to open the Meter case or replace any parts, read the
instruction in this manual first. Do not perform these actions unless you
are qualified to do so.
When replacing fuses, use only the same type and same rating as
specified.
Do not try to operate the Meter if it is damaged. Disconnect the power
from the equipment and consult the local service representative. Return
the product to PICOTEST service department if necessary.
1.6 Symbols and Terms
This symbol indicates hazards that may cause damages to the
instrument or even result in personal injury.
This symbol indicates high voltage may be present. Use extra caution
before taking any action.
This symbol indicates the frame or chassis terminal presented need
to be connected to the actual earth ground.
This symbol indicates “Protective Conductor Terminal”.
This symbol indicates earth (ground) terminal.
This symbol indicates this product complies with the essential
requirements or the applicable European laws or directives with
respect to safety, health, environment and consumer protections.

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2General Maintenance
2.1 Setting Line Voltage and Replacing Fuse
Before turning on the multimeter, you should check the Line voltage setting
and the power-line fuse. If the line voltage setting is not properly, correct it.
If the power–line fuse is not good, replace a new one in the same type. The
following sections will show you how to do.
Warning! Before changing the line voltage setting or replacing the
power line fuse, make sure the multimeter is disconnected from the AC
power and remove all the test leads connected to it. An incorrect voltage
setting may cause severe damage to your instrument.
2.1.1 Voltage Selector
Normally, the line voltage is selected for your country properly when the
multimeter is shipped from the factory. Refer to your local power utility
voltage to see if the setting is correct. Follow the steps below to select a
properly line voltage for your instrument if the setting is not fit your
requirement.
NOTE:In some areas, the power utility voltage is 240V or 120V; in others,
it is 220 V or 100 V. The equipments are set properly according to users’
requirements when they are shipped from the factory. For more information,
please refer to section 2.1.2.
[Step 1]
Verify current line voltage setting from the window. If it is incorrect, you
must change it to a properly value. The position of the window is shown in
Figure 2-1.

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[Step2]
Turn off the power and disconnect the line cord from your multimeter as
shown in Figure 2-1. Also, you should remove all the leads connected to it.
Figure 2-1
[Step 3]
Open the cap and remove the voltage setting selector from the right middle
seam as shown in Figure 2-2. (You might need a flat-blade screwdriver to
do so.)
Figure 2-2
Window

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[Step 4]
Turn the voltage selector over, the value you want to set must in the right
side.
Figure 2-3
[Step 5]
Insert the voltage setting selector back into the socket and close the cap as
shown in Figure 2-4. Check the setting from the window again.
Figure 2-4
NOTE:Before re-connecting the power line cord to your multimeter, make
sure that power switch is in the “POWER OFF” state.

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2.1.2 Transformer
Usually you can change the line voltage setting by voltage selector as the
shown in section 2.1.1. If the voltages shown in the selector do not fit your
requirement, you may change the transformer connections to change the
line voltage setting selections. The voltages can be set for M3500A are 100,
120, 220, 240 Vac.
Warning! Do not perform this action unless you are qualified to do so.
For more information, please contact your local service representative.
[Step 1]
Turn off the power and disconnect the line cord from your multimeter as
shown in Figure 2-5. Also, you should remove all the leads connected to it.
Figure 2-5
[Step 2]
Remove the handle and then the metal cover. Please refer to section 4.2 for
more detail.
Warning! Do not open the case unless disconnecting the AC line cord
and all test leads. Do not perform this action unless you are qualified to do
so.

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[Step 3]
There are four wires in different colors on the transformer. Two of them
connect to the power entry according to the regular line voltage selections
for your country as shown in Figure 2-8.
Figure 2-8
[Step 4]
Please refer to the Table 2-1 to connect the wires for your need.
Figure 2-9
Power Line Voltage Wire color
100 Vac Brown
120 Vac Red
220 Vac Orange
240 Vac Yellow
Table 2-1
Power Entry
Transformer

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[Step 5]
Recover the case of the multimeter and then follow the steps in section
2.1.1 to set the desired line voltage.
NOTE: After transformer wiring modification, you should change the sticker
on voltage setting selector also. PICOTEST will provide the stickers for free.
Please contract your local service representative for the stickers for your
requirement.
2.1.3 Power Line Fuse
A power-line fuse located next to the AC receptacle (in the line voltage
selector) protects the power line input of the instrument. Verify that the
power-line fuse is good and replace a new one if it is damaged. The
multimeter is shipped from the factory with a fuse 0.25 A / 250 V, slow-blow,
5
×
20 mm (Picotest part number: 024-001-000004, the reference number:
FS102) installed. This is the correct fuse type for all line voltage settings.
Please follow the steps below to change the fuse.
[Step 1]
Turn off the multimeter and disconnect the line cord as shown in Figure 2-9.
Also, you should remove all the test leads that connected to your
instrument.
Figure 2-9

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[Step 2]
Open the cap and remove the voltage setting selector from the right middle
seam as shown in Figure 2-10. (You might need a flat-blade screwdriver to
do so.)
Figure 2-10
Warning! For continued protection against fire or instrument damage,
only replace fuse with the same type and rating. If the instrument
repeatedly blows fuses, locate and correct the cause of the trouble before
replacing the fuse.
[Step 3]
Remove the broken fuse from the selector and replace a new one as shown
in Figure 2-11. You must replace the fuse with the same type or same
rating.
Figure 2-11

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[Step 4]
Insert the voltage setting selector back into the socket and close the cap as
shown in Figure 2-12.
Figure 2-12
Warning!Before re-connecting the power line cord to your multimeter,
make sure that power switch is in the “POWER OFF” state. Verify if the line
voltage setting is correct before you turn on your instrument.
2.2 Current Input Fuse – 3.15 A
There are two fuses located in the front and rear current input terminals to
protect your multimeter against damage of strong current pulse. The front
and rear current input fuses used in M3500A are the type 3.15A, 250 V, 5
×
20 mm, fast acting, HBC and Ceramic Tube with high breaking character
(Picotest part number: 024-001-000007, the reference number: FS101). If
you need to replace them, please follow the steps shown below.
Warning! For continued protection against fire or instrument damage,
only replace fuse with the same type and rating. If the instrument
repeatedly blows fuses, locate and correct the cause of the trouble before
replacing the fuse.

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[Step 1]
Turn off the multimeter and disconnect the power line cord as shown in
Figure 2-13. Also, you should remove all the test leads that connected to
your instrument.
Figure 2-13
[Step 2]
Push the current input terminal and turn it right as shown in Figure 2-14 .
Figure 2-14
[Step 3]
Pull out the terminal (fuse holder) gently and you will find the current input

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fuse as shown in Figure 2-15.
Figure 2-15
[Step 4]
Remove the broken fuse and replace a new one with the same type or same
rating as shown in Figure 2-16.
Figure 2-16
[Step 5]
Insert the fuse holder back and turn it left as shown in Figure 2-17. Make
sure the fuse holder is properly seated and secured.
Current input Fuse
Fuse
Current Fuse Holder

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Figure 2-17
Warning!Before re-connecting the power line cord to your multimeter,
make sure that power switch is in the “POWER OFF” state.
NOTE: The rear current input fuse can be replaced by the same method as
the front one.
2.2.1 Current Input Fuse – 7 A
The current input Fuse provides an additional level of current protection
(The diagram in the below Figure 2-18 would let you know the function
more clearly). The fuse in M3500A is the type 7A, 5 x 20 mm, fast acting and
Ceramic Tube (Picotest part number: 024-001-000006, the reference
number: FS103). To replace the fuse, you have to release a holder by a
flat-blade screwdriver as shown in the following.

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Figure 2-18
[Step 1]
Turn off the multimeter and disconnect the power line cord as shown in
Figure 2-19. Also, you should remove all the test leads that connected to
your instrument.
Figure 2-19
[Step 2]
Please use a flat-blade screwdriver with a suitable pushing strength to turn
it left for releasing the holder.

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Figure2-20
[Step 3]
Pull out the terminal (fuse holder) gently and you will find the current input
fuse as shown in Figure 2-21.
Figure 2-21
[Step 4]
Remove the broken fuse and replace a new one with the same type or same
rating as shown in Figure 2-22.
Current input Fuse