SDM3055
Digital Multimeter

Service Manual
SM06035-E01C

Guaranty and Declaration
Copyright
SIGLENT TECHNOLOGIES CO., LTD All Rights Reserved.

Trademark Information
SIGLENT is the registered trademark of SIGLENT TECHNOLOGIES CO.,LTD

Declaration⚫

SIGLENT products are protected by patent law in and outside of P.R.C.

⚫

SIGLENT reserves the right to modify or change parts of or all the
specifications or pricing policies at company’s sole decision.

⚫

Information in this publication replaces all previously corresponding
material.

⚫

Any way of copying, extracting or translating the contents of this manual is
not allowed without the permission of SIGLENT.

⚫

SIGLENT will not be responsible for losses caused by either incidental orconsequential in connection with the furnishing, use or performance of thismanual as well as any information contained.

Product Certification
SIGLENT guarantees this product conforms to the national and industrial
standards in china as well as the ISO9001: 2015 standard and the ISO14001:
2015 standard. Other international standard conformance certification is inprogress.

General Safety Summary
Review the following safety precautions to avoid personal injuries and prevent
SDM3055 Service Manual Idamages to this product or any products connected to it. To avoid potential
hazards, use this product only as specified.
Only qualified personnel should perform service procedures.

To Avoid Fire or Personal Injuries
Use Proper Power Cord. Use only the power cord specified for this productand approved by local state.
Avoid Electric Shock. To avoid injuries or losses of life, do not connect ordisconnect probes or test leads while they are connected to a voltage source.
Ground the Product. This product is grounded through the protective terra
conductor of the power line. To avoid electric shock, the grounding conductor
must be connected to the earth. Make sure the instrument is grounded
correctly before connecting its input or output terminals.
Connect the Probe Properly. Do not connect the probe ground lead to a highvoltage since it has the isobaric electric potential as ground.
Observe All Terminal Ratings. To avoid fire or shock hazard, observe all
ratings and markers on the instrument and check your manual for more
information about ratings before connecting.
Use Proper Fuse. Use only the specified fuse.
Do Not Operate Without Covers. Do not operate this instrument with covers
or panels removed.
Avoid Circuit or Wire Exposed. Do not touch exposed junctions andcomponents when the unit is powered.

II SDM3055 Service ManualDo Not Operate With Suspected Failures. If you suspect damage occurs tothis instrument, have it inspected by qualified service personnel before
further operation. Any maintenance, adjustment or replacement especially tothe circuits or accessories should be performed by SIGLENT authorized
personnel.
Keep Product Surfaces Clean and Dry.
Do Not Operate in Wet/Damp Conditions. To avoid electric shock, do not
operate the instrument in wet or damp condition.
Do Not Operate in an Explosive Atmosphere. To avoid injuries or fire
hazards, do not operate in an explosive atmosphere.

Safety Terms and Symbols
Terms on the Product. These terms may appear on the product:
DANGER: Indicates an injury or hazard that may immediately happen.
WARNING: Indicates an injury or hazard may be accessible potentially.
CAUTION: Indicates damage to the instrument or other property may occur.
Symbols on the Product. These symbols may appear on the product:

SDM3055 Service Manual III

Catalog
Guaranty and Declaration ..................................................................................................... IGeneral Safety Summary ..................................................................................................... IGeneral Features and Specifications .................................................................................. 1
General Features.......................................................................................................... 1
Specifications ............................................................................................................... 2
Prepare Information ............................................................................................................. 7
Functional checking ...................................................................................................... 7
Power-on Inspection ............................................................................................. 7
Default Setup......................................................................................................... 7
Self Test ................................................................................................................. 8
Performance Verification ..................................................................................................... 9
Performance verification test items .............................................................................. 9
Recommended Test Equipment ................................................................................... 9
Performance verification step ....................................................................................... 9
Test Considerations .................................................................................................... 10
Zero Offset Verification ............................................................................................... 10
DC Voltage and DC Current Gain Verification ........................................................... 10
Frequency Accuracy Verification ................................................................................ 11
AC Voltage and AC Current Verification ..................................................................... 12
Capacitance Verification ............................................................................................. 13
Assembly Procedures ........................................................................................................ 14
Security Consideration ............................................................................................... 14
Required Tools ............................................................................................................ 14
Disassembly Procedures............................................................................................ 15
Troubleshooting ................................................................................................................. 19
ESD Precautions ........................................................................................................ 19
Required Equipments ................................................................................................. 19
Analog Board Drawing ............................................................................................... 20
Main Board Drawing ................................................................................................... 21
Check the Power Supply ............................................................................................ 22
Check the Analog Board............................................................................................. 23
Voltage Checking ................................................................................................ 23
Analog board Clock Checking ............................................................................. 24
Check the Main Board ................................................................................................ 25
Voltage Checking ................................................................................................ 25
Microprocessor Checking.................................................................................... 25
Quick Guide for General Failures ............................................................................... 26
Maintenance ...................................................................................................................... 26
Maintain Summary...................................................................................................... 26
Repackaging for Shipment ......................................................................................... 27
Contact SIGLENT .............................................................................................................. 28
IV SDM3055 Service ManualGeneral Features and Specifications
SDM3055 is a 5½ dual-display instrument designed with 5½ digits readings
resolution and dual-display, especially fitting to the needs of high-precision,
multifunction, and automation measurements. It realized a combination ofbasic measurement functions, multiple math functions, and display functions,etc.

General Features⚫

4.3 inch color TFT-LCD display screen with 480*272 high resolutions⚫

Real 5½ digits readings resolution⚫

Up to 150rdgs/S measurement speed⚫

True-RMS AC Voltage and AC Current measurements⚫

1 Gb Nand Flash size, mass storage configuration files and data files⚫

Built-in cold terminal compensation for thermocouple⚫

Support standard SCPI and control software on PC, compatible withcommands of main stream multimeters⚫

Supports dual-display function, Chinese and English menu⚫

Built-in help system, convenient to acquire information⚫

Support USB Device, USB Host, LAN, and USB-GPIB (Option) interfaces⚫

Configuration and measured data can be imported or exported via VXI 11,
USBTMC and USB flash drive, which is convenient for users to modify,
view and backup

SDM3055 Service Manual 1

Specifications
DC Characteristic
Accuracy±（% of Reading + % of Range）[1]Temperature
coefficient
Function

Range[2]Test current or
Load voltage

1 Year
23℃±5℃

0℃～18℃
28℃～50℃

DC Voltage

200 mV

0.015+ 0.004

0.0015+ 0.0005

2V

0.015+ 0.003

0.0010+ 0.0005

20 V

0.015+ 0.004

0.0020+ 0.0005

200 V

0.015+ 0.003

0.0015+ 0.0005

1000 V[4]0.015+ 0.003

0.0015+ 0.0005

200 μA< 8 mV

0.055+ 0.005

0.003+ 0.001

2 mA< 80 mV

0.055+ 0.005

0.002+ 0.001

20 mA< 0.05 V

0.095+ 0.020

0.008+ 0.001

200 mA< 0.5 V

0.070+ 0.008

0.005+ 0.001

2A< 0.1 V

0.170+ 0.020

0.013+ 0.001

10 A[5]< 0.3 V

0.250+ 0.010

0.008+ 0.001

200 Ω

1 mA

0.030+ 0.005

0.0030+ 0.0006

2 KΩ

1 mA

0.020+ 0.003

0.0030+ 0.0005

20 KΩ

100 μA

0.020+ 0.003

0.0030+ 0.0005

200 KΩ

10 μA

0.020+ 0.010

0.0030+ 0.0005

2 MΩ

1 μA

0.040+ 0.004

0.0040+ 0.0005

10 MΩ

200 nA

0.250+ 0.003

0.0100+ 0.0005

100 MΩ

200 nA || 10 MΩ

1.75+ 0.004

0.2000+ 0.0005

Diode Test

4.0 V[6]1 mA

0.05+ 0.01

0.0050+ 0.0005

Continuity Test

2000 Ω

1 mA

0.05+ 0.01

0.0050+ 0.0005

DC Current

Resistance[3]Remarks:[1] Specifications are for 0.5 Hour warm-up, “Slow” measurement rate and calibration
temperature 18℃～28℃.
[2] 20% over range on all ranges except for DCV 1000 V, ACV 750 V, DCI 10 A and ACI
10 A.
[3] Specifications are for 4-wire measure or 2-wire measure under “REF” operation. ±0.2Ω
of extra errors will be generated if perform 2-wire measure without “REF” operation.
[4] Plus 0.02 mV of error per 1 V after the first ±500 VDC.
[5] 30 seconds OFF after 30 seconds ON is recommend foe the continuous current thathigher than DC 7 A or AC RMS 7 A.
2 SDM3055 Service Manual[6] Accuracy sepcifications are only for voltage measuring at input terminal. The typicalvalue of current under measure is 1 mA. Voltage drop at diode junction may vary withcurrent supply.

AC Characteristic
Accuracy±（% of Reading + % of Range）[1]Temperature
coefficient
Function

Range[2]Frequency Range

1Year
23℃±5℃

0℃～18℃
28℃～50℃

200 mV

2V

True-RMSAC Voltage [3]

20 V

200 V

750 V

20 mA
True-RMS
AC Current [4]200 mA

2A

20 Hz – 45 Hz

1.5 + 0.10

0.01 + 0.005

45 Hz – 20 KHz

0.2 + 0.05

0.01 + 0.005

20 KHz – 50 KHz

1.0 + 0.05

0.01 + 0.005

50 KHz –100 KHz

3.0 + 0.05

0.05 + 0.010

20 Hz – 45 Hz

1.5 + 0.10

0.01 + 0.005

45 Hz – 20 KHz

0.2 + 0.05

0.01 + 0.005

20 KHz – 50 KHz

1.0 + 0.05

0.01 + 0.005

50 KHz –100 KHz

3.0 + 0.05

0.05 + 0.010

20 Hz – 45 Hz

1.5 + 0.10

0.01 + 0.005

45 Hz – 20 KHz

0.2 + 0.05

0.01 + 0.005

20 KHz – 50 KHz

1.0 + 0.05

0.01 + 0.005

50 KHz –100 KHz

3.0 + 0.05

0.05 + 0.010

20 Hz – 45 Hz

1.5 + 0.10

0.01 + 0.005

45 Hz – 20 KHz

0.2 + 0.05

0.01 + 0.005

20 KHz – 50 KHz

1.0 + 0.05

0.01 + 0.005

50 KHz –100 KHz

3.0 + 0.05

0.05 + 0.010

20 Hz – 45 Hz

1.5 + 0.10

0.01 + 0.005

45 Hz – 20 KHz

0.2 + 0.05

0.01 + 0.005

20 KHz – 50 KHz

1.0 + 0.05

0.01 + 0.005

50 KHz –100 KHz

3.0 + 0.05

0.05 + 0.010

20 Hz – 45 Hz

1.5 + 0.10

0.015 + 0.015

45 Hz – 2 KHz

0.50 + 0.10

0.015 + 0.006

2 KHz – 10 KHz

2.50 + 0.20

0.015 + 0.006

20 Hz – 45 Hz

1.5 + 0.10

0.015 + 0.005

45 Hz – 2 KHz

0.50 + 0.10

0.015 + 0.005

2 KHz – 10 KHz

2.50 + 0.20

0.015 + 0.005

20 Hz – 45 Hz

1.5 + 0.20

0.015 + 0.005

45 Hz – 2 KHz

0.50 + 0.20

0.015 + 0.005

SDM3055 Service Manual 3

10 A

[5]

2 KHz – 10 KHz

2.50 + 0.20

0.015 + 0.005

20 Hz – 45 Hz

1.5 + 0.15

0.015 + 0.005

45 Hz – 2 KHz

0.50 + 0.15

0.015 + 0.005

2 KHz – 10 KHz

2.50 + 0.20

0.015 + 0.005

Additional wave crest factor error ( not Sine ) [6]
Wave crest coefficient

Error（% Range）

1-2

0.05

2-3

0.2

Remarks:[1] Specifications are for 0.5 Hour warm-up, “Slow” measurement rate and calibration
temperature 18℃～28℃.
[2] 20% over range on all ranges except for DCV 1000 V, ACV 750 V, DCI 10 A and ACI
10 A.
[3] Specifications are for amplitude of sine wave input > 5% of range. For inputs from 1%
to 5% of range and <50 kHz, add 0.1% of range extra error. For 50 kHz to 100 kHz,
add 0.1% of range extra error.
[4] Specifications are for sine wave input > 5% of range. 0.1% errors wills be added when
the range of input sine wave is 1% to 5% .
[5] 30 seconds OFF after 30 seconds ON is recommend foe the continuous current thathigher than DC 7 A or AC RMS 7 A.
[6] Specifications are for frequency of input < 100Hz

Frequency and Period Characteristic
Accuracy±（% of Reading + % of Range）[1]Temperature
coefficient
Function

Range

Frequency Range

1 Year
23℃±5℃

0℃～18℃
28℃～50℃

Frequency

200 mV to 750 V[2]4 SDM3055 Service Manual

20 Hz – 2 KHz

0.01+0.003

0.002+0.001

/Period

2 KHz – 20 KHz

0.01+0.003

0.002+0.001

20 KHz – 200 KHz

0.01+0.003

0.002+0.001

200 KHz –1 MHz

0.01+0.006

0.002+0.002

Remarks:[1] Specifications are for 0.5 Hour warm-up.
[2] Except for special marks, the AC input voltage is 15% to 120% of range when <100
kHz and 30% to 120% of range when >100 kHz. 750 V range is limited to 750 Vrms.

Capacitance Characteristic
Accuracy±（% of Reading + % of Range）[1]Temperature
coefficient
Function

Max Testing
Current

Range[2]1 Year
23℃±5℃

0℃～18℃
28℃～50℃

Capacitance

2 nF

200 nA3+1.0

0.08+0.002

20 nF

200 nA

1+0.5

0.02+0.001

200 nF

2 μA

1+0.5

0.02+0.001

2 μF

10 μA

1+0.5

0.02+0.001

200 μF100 μA

1+0.5

0.02+0.001

10000 μF

1 mA

2+0.5

0.02+0.001

Remarks:[1] Specifications are for 0.5 Hour warm-up and “REF” operation. Using of non-film
capacitor may generate additional errors.
[2] Specifications are for from 1% to 120% on 2 nF range and ranges from 10% to 120%on other ranges.

Temperature Characteristic
Accuracy±（% of Reading + % of Range）[1]Function

Probe
Type

Probe
Model

Working
Temperature
Range

1Year
23
℃
±5℃

Temperature
coefficient
0℃～18℃
28℃～50℃

SDM3055 Service Manual 5

RTD[2]α=0.00385
B
E
JK

Temperature
TC[3]

N
R
S
T

-200℃至 660℃
20℃～1820℃-270℃～1000℃-210℃～1200℃-270℃～1370℃-270℃～1300℃-50℃～1760℃-50℃～1760℃-270℃～400℃

0.16℃

0.08+0.002

0.76 ℃

0.14℃

0.5℃

0.02℃

0.5℃

0.02℃

0.5℃

0.03℃

0.5℃

0.04℃

0.5℃

0.09℃

0.6℃

0.11℃

0.5℃

0.03℃

Remarks:[1] Specifications are for 0.5 Hour warm-up, not include probe error.
[2] Specifications are for 4-wire measure or 2-wire measure under “REF” operation.
[3] Built-in cold terminal compensation for thermocouple, accuracy is ±2℃.

6 SDM3055 Service ManualPrepare Information
Before doing performance verifying or procedure adjusting, you should masterthe following operations to make the mulimeter work in a good state or deal
with some simple functional problems. The following contents are included inthis chapter:⚫

How to perform functional checks⚫

How to use self-test routine⚫

How to recall factory Default settings

Fore more detailed information about oscilloscope operation, please refer toyou Quick Guide for SDM3055.

Functional checking
This functional checking covers three kinds of checks, by which you can verify
whether the mulimeter is working correctly.

Power-on Inspection
Before connect the instrument to a power source, please select the AC voltage
selector on the rear panel of your multimeter according to the power supply.
Then connect the power line to the socket on the rear panel of the mutimeter.
Note: to avoid electric shock, make sure that the instrument is correctly
grounded to the earth before connecting AC power.
The boot screen appears after pressing the power-on button. Then perform
following operation, the intrument can be restored to factory default settings:
Press [Shift] > [Utility] > Store/Recall >Set To Defaults

Default Setup
After setting to defaults, multimeter is set to DC voltage measurements. Other
default Settings are shown in the following table.

SDM3055 Service Manual 7

Default settings
Menu or System

DCV

AcquireMath
Display
Hold

OptionDefault setting

Range
Speed
FilterRel
Trg Src
Delay
Samples/Trigger
VMC Out
Statistics
LimitsdB/dBmRef Value
Display
Probe Hold

Auto
Slow
Off
Off
Auto
Auto
1
Pos
Hide
Off
Off
Off
NumberOff

Self Test
SDM3055 provides self-test functions, including Key Test, LCD Test, Beeper
Test and Chip Test.
Operating Steps:
1. Press [Shift] > [Utility] > Test /Admin > Board Test
2. Test the keys:
Select Key to enter the key test interface. The on-screen lathy rectangle
shapes represent the keys on the front panel. Test all keys and knobs andyou should also verify that all the backlit buttons illuminate correctly.
3. Test the LCD screen:
Select LCD to enter the screen test interface, the screen shows themessage:” Press ‘Change’ to change Press ‘Done’ to “Exit”. Press Change
to start the test and observe if the screen has severe color or other display
error.
4. Test the beeper:
Press Beeper to test the beeper. Under regular circumstance, press
Beeper one time and the instrument will beep one time.
5. Test the chips:
Press Chip > Start to start chip test. Determine whether the chip test passaccording to the interface message.

8 SDM3055 Service ManualPerformance Verification
Use the performance verification tests in this section to verify the measurement
performance of the instrument using the instrument’s specifications listed in the
product data sheet. Performance verification tests are recommended as an
acceptance test when you first receive the instrument or after performing
calibration. If the instrument fails performance verification, calibration
adjustment or repair is required.

Performance verification test items
⚫
⚫
⚫
⚫
⚫

Zero Offset Verification
DC Voltage and DC Current Gain Verification
Frequency Accuracy Verification
AC Voltage and AC Current VerificationHigh Current Verification
Capacitance Verification

Recommended Test Equipment
The recommended test equipment for the performance verification andcalibration is listed below. If the exact instrument is not available, substitutecalibration standards of equivalent accuracy.
Application

Recommended Equipment

Zero Offset Verification

Keysight 34172B

DC Voltage and DC Current Gain
Verification

Fluke 5522A

Frequency Accuracy Verification

Siglent SDG2000X SeriesFunction/Arbitrary
Waveform Generator

AC Voltage and AC Current
Verification

Fluke 5522A

Capacitance Verification

Fluke 5522A

Performance verification step
1. Connect the calibrator to the input terminals correctly.
2. Configure each function and range in the order shown in the tablecorresponding to the DMM model number. Provide the input shown in thetable.
3. Make a measurement and return the result. Compare measurement results
to the test limits shown in the table. (Be certain to allow for appropriate
source settling.)
SDM3055 Service Manual 9Test Considerations⚫
⚫
⚫
⚫

Ensure that the test ambient temperature is stable and between 18°C and
28°C. Ideally the calibration should be performed at 23°C±2°C.
Ensure ambient relative humidity is less than 80%.
Allow a 30 minute warm–up period with a copper short connected.
Ensure the measuring rate is set to “slow” for DCV, ACV, DCI, ACI and
2-Wire/ 4-Wire Resistance measurement.

Zero Offset Verification
Input

FunctionOpen

DC Current

Short

Short

DC Volts

4-wire Ohms

Range

Error from Nomina(1 years)l

200μA±0.01μA

2mA±0.1μA

20mA

±4μA

200mA

±16μA

2A

±400μA

10A

±1mA

200mV

±8μV

2V

±100μV

20V±800μV

200V

±6mV

1000V

±30mV

200Ω

±10mΩ

2kΩ

60mΩ

20kΩ

600mΩ

200kΩ

6Ω

2MΩ

80Ω

20MΩ

300Ω

100MΩ

4kΩ

DC Voltage and DC Current Gain Verification
Input
Voltage

Function

Range

Error from Nominal(1 years)-200mVDC Volts

200mV

±38μV

10 SDM3055 Service Manual

200mV-2V

2V

2V±400μV

10V±2.3mV-20V

20V±3.8mV

20V
-200V

200V

200V
-500V

±36mV
±110mV

1000V

1000V

±180mV

Input
Range

Error from Nominal(1 years)

200μA

200μA

±0.12μA

2 mA

2mA±1.2μA

20mA

±23μA

200mA

±158μA

2A

2A±3.8mA

10A

10A

±26mA

Current

Function

20mA

DC Current

200mA

Input
Range

Error from Nominal(1 years)

200Ω

200Ω

±70mΩ

2kΩ

2kΩ

±460mΩ

20kΩ

±4.6Ω

200kΩ

±46Ω

2 MΩ

2 MΩ

±880Ω

10 MΩ

10 MΩ

±25.3kΩ100MΩ

±1.754 MΩ

Resistance

20kΩ
200kΩ

100MΩ

Function

4-wire Ohms

2-wire Ohms

Frequency Accuracy Verification
Input
Vrms

Frequency

Range

Error from Nominal(1 years)

60mV

500kHz

200mV

±50Hz

0.3V

20Hz

2V

±0.2Hz

SDM3055 Service Manual 11

AC Voltage and AC Current Verification
Input
Vrms

Frequency

Range

1kHz
200mV

2V

50kHz

Error from Nominal(1 years)±500μV

200mV±2.1mV

100kHz

6.1mV

1kHz

±5 mV

50kHz

2V

±21 mV

100kHz±61 mV

0.2V

1kHz±30.4mV

2V

1kHz

±34mV

45Hz
20V

200V

20kHz

20V

±320mV
±50mV

50kHz

±210mV

100kHz±610mV

1kHz±500mV

50kHz

200V

±2.1V

100kHz

±6.1V

750V

1kHz

±1.88V

250V

50kHz

75V

100kHz

±3.6V

Input

Error from Nominal(1 years)

Irms
20mA
2mA
200mA
20mA
2A
200mA
10A

Frequency
1kHz
10kHz

750V

Range
20mA

1kHz
1kHz

±2.88V±0.12 mA
±0.54mA±0.41 mA

200mA

±1.2 mA

10kHz±5.4 mA

1kHz±6.1 mA

1kHz

2A±14 mA

10kHz±54 mA

1kHz±26 mA

1kHz

10A

10kHz

12 SDM3055 Service Manual±65 mA±270 mA

Capacitance Verification
Input
Capacitance
2nF
20nF
200nF
2μF
20μF

Range
2nF
20nF
200nF
2μF
20μF

Error from Nominal(1 years)±0.08nF±0.3nF±3nF±30nF±300nF

200μF

200μF

±3μF

10000μF

10000μF±250μF

SDM3055 Service Manual 13

Assembly ProceduresThis chapter describes how to remove the major modules from the SDM3055
series generator. To install the removed modules or replace new modules,
please follow corresponding operating steps in reverse order.

Security Consideration
Only qualified personnel should perform the disassembly procedures.
Whenever possible, disconnect the power before removing or replacing.
Otherwise, personal injuries or damages to the components may occur.
Avoid Electric Shock Hazardous voltages exist on the LCD module andpower supply module. To avoid electrical shock, disconnect the power cordfrom the generator, and then wait at least three minutes for the capacitors in
the generator to discharge before beginning the disassembly.
Preventing ESD Almost all electrical components can be damaged byelectrostatic discharge (ESD) during handling. Component damages can occur
at electrostatic discharge voltages as low as 50 volts. The following guidelines
will help preventing ESD damage when servicing the instrument or any
electronic device.
◆ Disassemble instruments only in a static-free work area.
◆ Use a conductive work area to reduce static charges.
◆ Use a conductive wrist strap to reduce static charge accumulation.
◆ Minimize handling.
◆ Keep replacement parts in original static-free packaging.
◆ Remove all plastic, foam, vinyl, paper and other static-generating materials
from the immediate work area.
◆ Use only anti-static solder suckers.

Required Tools
Use these tools to remove or replace the modules in the generator:⚫

T10 hexagon screwdriver⚫

2# Phillips screwdriver⚫

needle-nose pliers

14 SDM3055 Service ManualDisassembly Procedures
1. Turn off the power and remove all measurement leads and other cables,
including the power cord, from the instrument before continuing.
2. Rotate the handle to the upright position and remove it by pulling outward
where it attaches to the case.

3. Unscrew the two captive screws in the rear bezel and remove the rearbezel as indicated by the arrow shown below

SDM3055 Service Manual 15

4. Remove the screw on the bottom of the instrument and place it in a safe
location for re-assembly. Slide off the instrument cover as indicated by
the arrow shown below.

5. Remove the cable plug(in the red circle and yellow box shown below)
connected to the main body

16 SDM3055 Service Manual

6. Unscrew the 5 captive screws in the rear metal cover and remove the rearmetal cover.

7. Unscrew the 4 screws and remove the fan.

8. Remove the cable plug connected to the front pannel.

9. Remove the cable and unscrew all the screws,then you can remove
thePCBA.
SDM3055 Service Manual 17

This concludes the disassembly procedure. To re-assemble the instrument,
reverse the procedure.

18 SDM3055 Service ManualTroubleshooting
The internal structure of the multimeter consists of analog board, main board
and power supply board, key and LCD board, and interface board. They arelinked through cables or connectors. This chapter explains the main checking
procedures for these three boards (mainly main board and analog board) bymeasuring the corresponding test points and checking the signals ofconnectors on them, thus to help in determining the reason for the failure thathas been encountered while operating the SDM3055 series digital mulimeter.

ESD Precautions
While performing any internal test of the multimeter, please refer to thefollowing precautions to avoid damages to its internal modules or components
result from ESD.
⚫

Touch circuit boards by the edges as possible as you can.

⚫

Reduce handling of static-sensitive modules when necessary.

⚫

Wear a grounded antistatic wrist strap to insulate the static voltage from.

your body while touching these modules.
⚫

Operate static-sensitive modules only at static-free areas. Avoid handling
modules in areas that allow anything capable of generating or holding astatic charge.

Required Equipment
The equipments listed in the table are required to troubleshoot the multimeter.
Table 6-1 required equipments

Equipment

Critical Specifications

ExampleAccuracy ±0.05%

Siglent SDM3045X

Digital Multimeter
1 mV resolution
Oscilloscope

200MHz Bandwidth

Siglent SDS2102X

SDM3055 Service Manual 19Analog Board Drawing
Analog board is a kind of signal sampling board for output digital signal. It
mainly works on signal processing such as AC is converted to DC in order tomeasure easily magnitude of AC. Please refer to the following drawing toquickly locate the test points on the analog board for easy resolution of the
failures you encounter.

20 SDM3055 Service Manual

Main Board Drawing
Main board is used to control and manage the whole internal system of themultimeter. It completes the GUI function, controlling and configuration function
for analog board as well as man-machine interaction. Please refer to thefollowing drawing to quickly locate the test points on the main board for easy
resolution of the failures you encounter.

SDM3055 Service Manual 21

Check the Power Supply
There are two power connectors through which the analog board and mainboard can be supplied electricity. For the analog board, there are three voltage
test points on its power connector. For the main board, there is one test point.
Before performing the power supply testing procedure, please make sure thatthe multimeter is grounded correctly through the protective lead of the power
cord. Take care not to touch or even disassemble the power supply module
without any safety precautions, or you may probably suffer from electric shockor burn. Here are procedures for testing the power supply:
1. Disconnect the power cord of the multimeter and then check whether thefuse has been burnt out.
2. Remove metal shell of the multimeter using a driver, and then disconnect thepower connector connected to the main board.
3. Focus on the Power Connector for analog board, which contains five pinsfrom Pin1 to Pin5. You can test the adjacent pins that are marked with blue,
brown, yellow and white to check whether the AC voltage value is within thecorresponding specified range using a digital multimeter. The voltage
parameters to be tested are listed in table below:
Table 6-2 Test AC voltages for the analog board power connector

Pins

Voltage value (V) Error limit (V)blue to blue

8

±1

Yellow to brown

16±2

White to yellow

16±2

Table 6-3 Test AC voltage for the main board power connector

PinsBlack to black

Voltage value (V) Error limit (V)8±1

If each tested voltage value is within the corresponding spec range referring to
the table above, then the power supply works normally. Otherwise, it proves tobe faulted, please return it to the factory to have it repaired or contact
SIGLENT.
Note: The main power supply provides an input fuse to protect against thedanger of fire in the event of a failure of the power supply circuitry. However,
22 SDM3055 Service Manualthis fuse will not fail ("open" or "blow") in normal power supply operation exceptthat a significant overload occurs. Replace the entire main power supply
assembly if the input fuse fails.

Check the Analog Board
If it is desired to remove the analog board from the metal shelf inside themultimeter, you’d better place it on a clean, insulated mat. Here are proceduresfor testing the analog board:
1. Several types of connectors are used on the analog board. Check to makecertain that all of these are connected properly.
2. After checking these connectors, then connect the generator to AC power
and power it on. Check if the voltage values at all test points are within thespecified range using a digital multimeter. The voltage parameters to betested are listed in table 5-3:

Voltage Checking
Test the voltage points on the analog board in the table below. To locate thetest points, please refer to the drawing of the analog board. If not each tested
voltage value is within the corresponding spec range referring to table 5-4, it
proves to be faulted, please return it to the factory to have it repaired or contact
SIGLENT.
Table 6-4 Test DC voltages of the analog board

Test point

Name

Test pin

Voltage value (V)Error limit(V)

T1

Q3

3

-22

±2

T2

Q1

3

+22

±2

T3

U2

1

-15

±0.5

T4

U3

1

+15

±0.5

T5

U707

4

+5

±0.3

T6

C244

cathode

-3.8

±0.3

T7

U710

4

+6.7

±0.3

T8

U705

4

+3.3

±0.2

GND

U705

1

SDM3055 Service Manual 23Analog board Clock Checking
Analog board clock is the internal system clock of the multimeter. To verify if
the clock on the analog board works normally, please test the clock frequency
listed below using an oscilloscope.
Table 6-5 Clock Source of the analog Board

Test point Name
T9

24 SDM3055 Service Manual

R24

Pin

Frequency Stability

1 or 2

12.8MHz±50ppmSIGLENT

Check the Main Board
If the main board does need to be removed from the metal shelf located inside
the generator, place it on a clean, insulated mat. Testing procedures for themain board are as follows:
1. Several types of connectors are located on the main board. Check if allthese are connected properly.
2. Make sure that the connectors on the main board are properly connected,
then connect the multimeter to AC power and turn it on. Check if the voltage
values at all test points are within the spec range using a digital multimeter.
The voltage parameters to be tested are listed in table 5-6:

Voltage Checking
Test the voltage points on the main board in the table below. To locate the test
points, please refer to the drawing of the main board. If not each tested voltage
value is within the corresponding spec range referring to table 5-6, it proves tobe faulted, please return it to the factory to have it repaired or contact
SIGLENT.
Table 6-6 Test DC voltages of the main board

Test point Name

Pin

Voltage value (V) Error limit (V)

TP1

J14

1 to 2

+8.6

±2

TP2

U14

4

+3.3

±0.1

TP3

U12

4

+5

±0.2

TP4

TP86

Solder

+16

±2

GND

SC16

Microprocessor Checking
Observe the LED light on the main board, which indicates the working state of
microprocessor chip. If the light turns on, then the corresponding codes havebeen loaded successfully and the chip is in an operating state. Otherwise,
there may be a problem with it.

SDM3055 Service Manual 25

Quick Guide for General Failures
The general hardware failures are described in the following. Reading thefollowing information can help you quickly handle some easy hardware failureswith more convenience.
1. No start-up after pressing the Power button:(1) Check if the power cord is correctly connected.
(2) Check if the power button is usable.
(3) Check whether the fuse has been burned out. If the fuse is blown,please replace with a fuse of the same rating.
(4) Check the connection between the power supply and the main board.
(5) If the instrument still does not work normally, please contact SIGLENT.
2. The instrument starts up with a dark screen:(1) Check the connection between the keypad circuit board and the mainboard.
(2) If the instrument still does not work normally, please contact SIGLENT.
3. No response after pressing any button or abnormal display of thescreen:(1) Check the connection between the keypad circuit board and the mainboard.
(2) If the instrument still does not work normally, please contact SIGLENT.

Maintenance
Maintain Summary
SIGLENT warrants that the products it manufactures and sells are free fromdefects in materials and workmanship for a period of three years from the dateof shipment from an authorized SIGLENT distributor. If a product provesdefective within the respective period, SIGLENT will provide repair or
replacement as described in the complete warranty statement.
To arrange for service or obtain a copy of the complete warranty statement,
please contact your nearest SIGLENT sales and service office.
Except that as provided in this summary or the applicable warranty Statement,
26 SDM3055 Service Manual

SIGLENT

SIGLENT makes no warranty of any kind, express or implied, including without
limitation the implied warranties of merchantability and fitness for a particularpurpose. In no case shall SIGLENT be liable for indirect, special orconsequential damages.

Repackaging for Shipment
If the unit needs to be shipped to SIGLENT for service or repair, be sure:
1. Attach a tag to the unit identifying the owner and indicating the required
service or repair.
2. Place the unit in its original container with appropriate packaging material
for shipping.
3. Secure the container with strong tape or metal bands.
If the original shipping container is not available, place your unit in a container
which will ensure at least 4 inches of compressible packaging material aroundall sides for the instrument. Use static-free packaging materials to avoid
additional damage to your unit.

SDM3055 Service Manual 27

Contact SIGLENTSIGLENT Technologies Co., Ltd
Building No.4 & No.5, Antongda Industrial Zone, 3rd Liuxian Road, Bao'an District,
Shenzhen, China
Tel:+ 86-755-3688-7876
Fax: + 86-755-3359-1582
E-mail: sales@siglent.com
Web: http://int.siglent.com/

SIGLENT Technologies NA, Inc
6557 Cochran Rd Solon, Ohio 44139
Tel: 440-398-5800
Toll Free: 877-515-5551
Fax: 440-399-1211
E-mail: info@siglent.com
Web: www.siglentna.com

SIGLENT Technologies Germany GmbH
Staetzlinger Str. 70, 86165 Augsburg, Germany
Tel: +49(0)-821-666 0 111 0
Fax: +49(0)-821-666 0 111 22
E-mail: info-eu@siglent.com
Web: www.siglenteu.com

28 SDM3055 Service Manual