7-0 Basic Active Product Troubleshooting Skill

Basic Troubleshooting Skill

Guide to troubleshooting techniques of Comba active products

2007 Comba Telecom, All Rights Reserved2

Objective To develop an understanding on some

basic troubleshooting techniques that can be employed with simple test tools.


Topics1. Introduction

i. Why the need for troubleshooting?ii. Fault Categoryiii. Test tools

2. Types of Troubleshooting Techniquesi. Visual Inspection ii. Test & Measurement methodiii. Comparison Method

3. Fault Tracing4. Fault Symptoms5. Alarm Check List


Introduction Troubleshooting is a problem solving

technique that systematically seeks out the root of the problem so that it can be rectified.

Why the need for troubleshooting? Identify genuine and bogus faults Reduce repair time & cost for return

goods Reduce network coverage downtime


Fault CategoryClassification of Faults: Hardware

Usually associated with active modules such as PSU, PA, LNA and MCU

Active modules are subjected high power and heat

RF Interferences Interferences caused by radio environment High PIM interferences

Software Software glitches appearing on OMT/OMC Can be resolve by applying software patches

Mechanical Damaged parts such as broken pins/PCB/connectors Dry contact due to poor soldering or loose connector


Test Tools Spectrum Analyzer with tracking generator function Rhode &

Schwarz, model FSH3 or equivalent 40dB Attenuator Signal Generator Rhode & Schwarz, model SML 03 or equivalent Digital Multimeter Flexible jumper cable with N-male connectors x2


Techniques Test & Measurement Method

Measures the DL and UL output power at the MT and DT port respectively

Check for abnormal or no output power level Measures the AC and DC voltages of the PSU

Comparison Method Swap out the suspected faulty module with a new module and

compare the before and after effect Use a spare unit as reference to determine which module is faulty


Techniques Visual Inspection

Visually check for burnt mark, water seepage, corroded or brokenparts, loose connectors and missing components

Check LED indicators on MCU board and PSU for alarms or abnormal operation

Determine type of alarms using OMT

Water near PSU

Corrosion on PCB


Techniques Signal Tracing

Trace the input signal at the output port of each module to identify the faulty module

1

2

A

B


Fault Symptoms DL / UL PA module faulty :

PA and PLL alarms activated No / poor network coverage in repeater/booster cell vicinity High call setup failure High drop calls

LNA faulty LNA alarm activated High call setup failure No / poor network coverage in repeater/booster cell vicinity


Fault Symptoms Main Control Unit faulty

Multiple alarms and corrupted data appearing on MCU Fail to connect to equipment via local and remote connections


Fault Symptoms Power Supply Unit faulty :

Power Down and Power Failure alarms activated Red LED flashing, Green LED off, clicking sound Fail to connect to equipment via local and remote connections No / poor network coverage in repeater/booster cell vicinity


Downlink PA Test

Set the signal generator to EUT inband DL Freq X and output power level to -70dBm

Set the Spectrum Analyzer to monitor centre frequency at Freq X

Measured peak signal level should be approx (-70dBm+Max Gain-30dB-2dBm) after passing through the 30dB attenuator

Repeat the test for other channels, if necessary

Configure the EUT as follows: PA Switch = ON. Downlink CH No.1 = Freq X. Downlink Post-ATT 1 = 0. Downlink Pre-ATT 1 = 0.

EUT

30dB


Uplink PA Test

EUT

30dB

Set the signal generator to EUT inbandUL Freq X and output power level to -80dBm

Set the Spectrum Analyzer to monitor centre frequency at Freq X

Measured peak signal level should be approx (-80dBm+Max Gain-30dB-2dBm) after passing through the 30dB attenuator

Repeat the test for other channels

Configure the EUT as follows: PA Switch = ON. Uplink CH No.1 = Freq X. Set all UL ATT = 0.


Power Supply Unit Test Measures main supply AC voltages 110/220V Measures DC voltages +5V,+9V and +25V

+9V+5V+25V

GND

PSU


Remote Connection Failure Symptom 1:

Modem LED is not flashing LED indicator L4/H3 on MCU board is on

Possible Causes: SIM card does not have circuit switch data Modem antenna is not connected

Remedy Actions: Activate circuit switch data for SIM card Connect an antenna to the DT port or to the modem antenna port

of the equipment



Number dialed is not in use or not available Busy tone

Possible Causes: Modem failed to log on to cellular network SIM card does not have circuit switch data Modem antenna is not connected High network traffic

Remedy Actions: Activate circuit switch data for SIM card Ensure L4(Red)/H3(Red) indicator on MCU board is off after MCU

completes initialization. If L4/H3 remains on, press the reset button on the MCU board to re-initialize modem


LED indicators layout on older generation MCU board

LED indicators layout on new generation MCU board

Remote Connection Failure

PSUDT Coupler ON/OFFSwitch

DistributionBoard

MCU

MT Coupler

Modem

DT MT



Connection via wireless modem is fine but fail to connect via PSTN modem

Possible Causes: Telephone line does not support circuit switch data SIM card has data feature enabled only

Remedy Actions: Configure the SIM card to accept voice call Ensure telephone line supports circuit switch data



Error message Read parameters failed (for CSP3 model)

Possible Causes: SIM card number not added to Phone No. Check List

Authorize users phone nos.


Remote Connection Failure Remedy Actions:

Add SIM card no into the list Disable the Phone No. Checking feature


Safety Precautions Remove power plug from socket before replacing the PSU Switch off PSU before changing out any electrical parts such as

MCU board, PA and LNA Use proper tools to remove any parts/modules Label the cables or connectors, if necessary, before removing

any faulty module Ensure that the correct spare module is used for replacement Ensure all connectors and cables are correctly connected before

turning on the equipment Apply a fresh layer of heat transfer silicon beneath the new

module to achieve optimum heat transfer via chassis body.


Component Layout (RA-2100)

ALARMS CHECK LIST


Alarm Check ListType of Alarm Possible Cause Remedy Action

Power Down /AC Power Failure

- AC breaker tripped - Reset breaker

- Mains power failure - Restore mains power supply

- Power Supply Unit(PSU) faulty

- Replace blown fuse / PSU

Power Failed /DC Power Fault

- PSU faulty or fuse blown - Replace blown fuse / PSU

MCU Battery Fault /Li-ion Battery Fault

- Batteries are over-discharged - Connect batteries to PSU for charging

- Batteries are damaged - Replace batteries

DL PA - Over drive of PA module - Increase DL ATT value

- DL PA module is faulty - Replace PA module



DL VSWR - RF cable is not properlyconnected to MT port

- RF cable is damaged

- Check connection between cable and MT port

- Sweep feeder cable and DASwith Site Analyzer.

Optical Tx/Rx - Optical transceiver is faulty

- Fiber optical cable is damaged

- Replace Optical transceiver module

- Replace fiber optical cable

Li-ion Battery Low - Battery voltage is below threshold setting

- Connect batteries to PSU for charging

PA Over-Temperature - PA modules over heateddue to high input power

- PA module may be faulty

- Reduce input power level

- Replace faulty PA module

UL LNA Fault - Damaged by high inputpower

- LNA is faulty

- Replace LNA



UL Working Channel PLL 1

- UL PLL circuit is faulty - Replace UL PA module

DL Working Channel PLL 1

- DL PLL circuit is faulty - Replace DL PA module

DL Output Power Low

- Downlink output signal is below Power Low Threshold (DL out)

- Weak/No DL signal received

- Low gain setting for DLPA

- Adjust Power Low Threshold (DL out) to a suitable value

- Ensure BTS is transmitting

- Reduce Master ATT (DL) to increase output power

DL Input Power Overload

- DL Input power levelexceeds threshold value

- DL input power too strong

- Reduce input power level

- Adjust DL Input Power Overload Threshold value



Chassis Lock/Door Open

- Chassis door is open

- Micro switch has drycontact

-Close chassis door

- Ensure micro switch is notobstructed.

Master/Slave Unit Link - No connection betweenMaster and Slave unit

- Check cable connection between Masterand Slave unit.

External - One or more of externalalarms are triggered

- Clear external alarms

The End

Thank youThank you

Basic Troubleshooting Skill ObjectiveTopicsIntroductionFault CategoryTest ToolsTechniquesTechniquesTechniquesFault SymptomsFault SymptomsFault SymptomsDownlink PA TestUplink PA TestPower Supply Unit TestRemote Connection FailureRemote Connection FailureRemote Connection FailureRemote Connection FailureRemote Connection FailureRemote Connection FailureSafety PrecautionsComponent Layout (RA-2100)ALARMS CHECK LISTAlarm Check ListAlarm Check ListAlarm Check ListAlarm Check ListThe End

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7-0 Basic Active Product Troubleshooting Skill