Bang & Olufsen BeoLab 20 User manual

BeoLab 20
Type 6791 – 6797, 6799
Service Manual - version 1.0
English
German, French, Italian, Spanish, Dutch, Japanese, Korean and
Simplified Chinese versions are available in the Retail System
This Service Manual must be returned
with the defective parts/back-up suitcase !
82.0
30.4
39.3

CONTENTS
Survey of modules ................................................................... 1.1
How to service ......................................................................... 1.2
Repair tips ................................................................................ 2.1
Fault flow chart ........................................................................ 2.5
Survey of plugs and pins ........................................................ 2.11
Adjustments - Final check after repair ...................................... 3.1
Replacement of modules .......................................................... 4.1
Specification guidelines for service use ..................................... 5.1
Block diagram .......................................................................... 6.1
Wiring diagram ........................................................................ 6.3
Available parts ......................................................................... 7.1
Change log:
Ver. 1.0 ................................................................. Original release

Survey of modules 1.1
Survey of modules
02.2
48.2
02.1
35.2
35.1
04
30
68
48.3
48.1
47
89
Modules
PCB02.1 Input Panel
PCB02.2 Connector Interface
PCB04 Power Supply
PCB30 Digital Sound Engine
PCB35.1 Amplier
PCB35.2 Amplier
PCB47 LED Indicator
PCB48.1 NTC
PCB48.2 NTC
PCB48.3 NTC
PCB68 Switch Panel
PCB89 Wireless Power Link Rx
Speaker units
Tweeter
Midrange
Woofer

1.2 How to service
How to service
Strategy
This product is to be serviced in the customer’s home.
The repair involves replacement of the module(s). The replaced modules must be
returned for repair at the Bang & Olufsen Module Repair department. Error codes
as well as an adequate fault description must be returned with each replaced part.
For this purpose, use the Exchange Module section in the Retail Order System. To
help the Bang & Olufsen Module Repair department it is very important to answer
the following questions:
1. Which software versions are used in the product?
2. What happens in the actual situation?
3. Error code, the error code contains data that may be used for repairing the
module(s) and must be returned with the defective module(s).
Handling the error code (error log).
a. Make a note of the error code on the Exchange Module section and print it.
b. Use the error code when troubleshooting.
c. Return the error code in the Retail Order System.
d. Before returning the product to the customer, clear the error code.
Preparations before service
Fault explanation and demonstration
Before troubleshooting is initiated, let the customer demonstrate the fault, if
possible.
Recommended tools for service
- Bang & Olufsen ServiceTool
- Static-protective field service
- White gloves
- Shoe covers
- Soft lint-free cloth for cleaning
- WiSpy (Wi-Spy DBx + Chanalyzer Pro)
- Product cover
- Protection stocking to protect the tweeter assembly and decoration ring
Final check after repair
The final check after repair describes the activities that are needed to ensure the
product will be returned in perfect condition to the customer.
Please refer to ‘Final check after repair’ section on page 3.6.

How to service 1.3
Warnings when handling
Static electricity
Static electricity may damage the product.
Static-protective field service kit
A static-protective field service kit must always be used when the product is
disassembled or modules are being handled, since the internal electronics are very
sensitive to static electricity.
Follow the instructions in the Service Manual and use the ESD-mat for both old
and new modules.
When mains voltage on the product is required, remove the connection between
the product and the ESD-mat. This is important to avoid getting injured by mains
voltage.
STATIC ELECTRICITY
MAY DESTROY THE
PRODUCT
ESD
ESD-Mat
Waste of Electrical and Electronic Equipment (WEEE)
Electrical and electronic equipment, parts and batteries marked with this symbol
must not be disposed of with normal household wastage; all electrical and
electronic equipment, parts and batteries must be collected and disposed of
separately.
Management methods for controlling pollution caused by Electronic Information Products
Component
name:
Hazardous substance
Pb Hg Cd Cr(VI) PBB PBDE
Aluminum parts ×ooooo
PCBA ×ooooo
Symbols used in the charts:
o Indicates all homogeneous materials’ hazardous substances content are below the
ST/T 11363–2006 MCV limit.
× Indicates that the hazardous substance content contained in any one of the
homogeneous materials of the part exceeded the MCV limits specified in the
standard SJ/T 11363-2006.

1.4

Repair tips – Fault ow chart 2.1
Repair tips
Check cables .................................................................................... 2.2
Check for newest SW ....................................................................... 2.2
Backup ............................................................................................. 2.2
Restore ............................................................................................. 2.2
Error Log .......................................................................................... 2.2
Autocalibrate .................................................................................... 2.2
LED indicator .................................................................................... 2.2
Description of LED indications ........................................................... 2.2
Product Information - Usage data ..................................................... 2.3
NTC module test ............................................................................... 2.3
Speaker unit test ............................................................................... 2.4
Sound test ........................................................................................ 2.4
Fault ow chart
No function and no LED indication .................................................... 2.5
LED indicator is ashing quickly orange ............................................. 2.7
No sound from speaker in a wired setup ........................................... 2.8
No sound from speaker in a wireless setup ........................................ 2.9
Missing, atttenuated or distorted sound from speaker and no error
indication in error logs .................................................................... 2.10
Survey of plugs and pins ................................................................. 2.11

2.2 Repair tips
Repair tips
Check cables
Always check all external cables as well as internal cables.
Check for newest SW
Always ensure to have the newest software version installed. This is done via the
ServiceTool. Select BeoLab 20 > Software > Automatic Software Update.
The ServiceTool also includes noise and sound sources for testing.
Backup
Before starting the fault nding activity make a complete backup of the product by
means of the ServiceTool (see under Repair > Chassis and follow the instructions).
Restore
After the fault nding activity make a complete restore of the product by means of
the ServiceTool (see under Repair > Chassis and follow the instructions).
Error Log
If an error occurs in the product it is recorded and saved in the error log. The error
log may be helpful in troubleshooting situations. Use the ServiceTool to read out
the error log.
Autocalibrate
Use the ServiceTool > Adjustments > Adjustments > Autocalibrate to check
the amplier output if sound is missing, attenuated or distorted and the error log
doesn’t give a useful explanation. If the autocalibration fails the error can be
located to an error in either the Digital Sound Engine, the amplier modles or the
connection in between. If the autocalibration is successful and sound is still faulty,
it is most likely caused by a speaker driver error or a faulty connection between
amplier modules and speaker drivers.
LED indicator
The LED at the top of the speaker indicates the state of the
product by changing colour (red/orange/green), ashing or
solid. If errors occur during operation, the product will enter an
error state and the LED will start ashing quickly orange.
Description of LED indications
Constant Flashing slowly Flashing quickly
Green Product switches On (10
sec. duration)
Software update is
on-going
Associate mode (only in wireless mode:
ready for pairing)
Orange --The product is failing. The product will
not revert to normal operation. In some
cases it can be resolved by disconnecting/
connecting the mains:
This could be:
- NTC is defective or disconnected.
- Digital Sound Engine is overheating.
- Calibration failed or has not been done
(ashing quickly orange/green).
Red The product is connected
to mains, the product is
switching off or the
product restarts after a
reset.
Not used Not used

Repair tips 2.3
Product Information - Usage data
Usage data is logged in the product which can be very useful information in
troubleshooting situations. Use the ServiceTool to read out the usage data.
Approach (ServiceTool)
Connect a service PC with ServiceTool. Follow the procedure below:
- Connect the ServiceTool to the SERVICE connector on the product as shown:
- Run ServiceTool.
- Be sure that ServiceTool is updated to the latest version. If not, upgrade and restart
ServiceTool.
- Select COM port - ATI COM port
- Scroll down to BeoLab section.
- Select BeoLab 20 and click Launch.
- Click on the PRODUCT tab (if not already shown).
- Click + next to each item to expand the menus.
- Click System Info -> Product ID (the information screen appears).
- Click the Read button and conrm that product data is read out on the screen.
This indicates successful communication between the product and the service PC.
NTC module test
Measure the resistance of the NTC module to determine if
the fault is caused by a defective speaker unit or the NTC
module.
It is recommended to measure on the terminals on the
back of the speaker unit. The NTC module must be
disconnected from the product.
The resistance of the NTC module at 22ºC (72ºF) is approximately 470 kΩ.
If the NTC module is outside the limits, it is defective and must be replaced.
I/O
FREE
WALL
CORNER
L
R
WL
ROLE POS.
RESET
POWER LINK R-INPUT-L IN-TOSLINK-OUT SERVICE

2.4 Repair tips
Speaker unit test
Measure the DC resistance of the speaker unit to determine if the fault is caused
by a defective speaker unit. It is recommended to measure on the terminals on the
speaker unit. The speaker units must be disconnected from the product.
Speaker unit Impedance Nominal resistance Limits
Tweeter 8 Ω 6.7 Ω ± 15%
Midrange 8 Ω 6.2 Ω ± 15%
Woofers *) 2 × 6 Ω 2 × 5.9 Ω ± 15%
*) Each Woofer has two coils.
If the speaker unit is outside the limits, it is defective and must be replaced.
Under normal conditions it is not necessary to replace the gaskets on the speaker
unit, unless they have been damaged by accident.
Sound test
It is possible to test each speaker unit/amplier to check the sound quality, and
determine whether the devices are faulty or healthy. For this purpose use ServiceTool
and refer to the test section.
The Sound Test section features a sound generator which allows the user to send
a pure sound directly to the speaker unit. This feature makes troubleshooting or
testing more easy and targeted.
- Run ServiceTool.
- Be sure that ServiceTool is updated to the latest version. If not, upgrade and restart
ServiceTool.
- Scroll down to BeoLab section.
- Select BeoLab 20 and click Launch.
- Click on the PRODUCT tab (if not already shown).
- Click + next to each item to expand the menus.
- Click Test -> Test Sound (the information screen appears).
- Follow the procedure in Service Tool.

Fault ow chart 2.5
Repair/replace
connection
Set role switch
Fault symptom:
No function and no LED indication
Possible causes:
Defective PCB02.1, Input Panel
Defective PCB04, Power Supply
Defective PCB30, Digital Sound Engine
Defective PCB35.1/2, Amplier
Incorrect role switch setting
Read out Error Log
and follow
instructions
thoroughly
OK?
Is loging eld in
ServiceTool
indicating:
“... failed to read
error codes ...” ?
Conrm mains
voltage
OK?
Replace cable or
re-establish con-
nection
No
Is the speaker in a
wireless setup
Conrm that the
wired connection
between speaker
and the source
product is OK
OK?
Conrm that the
wireless connec-
tion between the
speaker and the
transmitter is OK
OK?
Repair/setup the
wireless connection
Yes
Fault ow chart
Survey of plugs and pins - see page 2.11
Conrm that the
role switch setting
is correct
OK?
Conrm that the
role switch setting
is correct
OK?
Set role switch
Conrm
5V_SB = 5V at
PCB04, P14 pin 1
OK?
Disconnect cable
W2 from PCB04
P14
Conrm 5V_SB =
5V at PCB04, P14
pin 1
OK?
Conrm mains
voltages at PCB04,
P13 pin 1-2
OK?
Replace PCB04,
Power Supply
Fault in cable
connection
Repair/replace
connection
Replace PCB30,
Digital Sound
Engine
*
Go to
#1
Go to
#1
*
Use ServiceTool to
autocalibrate the
new module

2.6 Fault ow chart
No
Yes
Conrm
PS_ON = 3.3V at
PCB04, P14 pin 7
OK?
Conrm
P15V = 15V at
PCB04, P14 pin 5
OK?
Connect to a source via:
Power Link, TOSLINK or line-in signal
Set role switch to R or L
Replace PCB35.1,
Amplier
*
OK?
Replace PCB35.2,
Amplier
*
Conrm
+28V at PCB04,
P16 pin 1, 2 and
-28V at PCB04,
P17 pin 8, 9
OK?
Conrm
+28V at PCB04,
P16 pin 1, 2 and
-28V at PCB04,
P15 pin 8, 9
OK?
Replace PCB30,
Digital Sound
Engine
Use ServiceTool to
calibrate the new
module
OK?
Replace PCB04,
Power Supply
OK?
Replace PCB02.1,
Input Panel
Remount PCB04,
Power Supply and
replace PCB30,
Digital Sound
Engine
Replace PCB04,
Power Supply
Replace PCB04,
Power Supply
Disconnect W8 from PCB35.2, P3.
Conrm +28V at PCB04, P17 pin 1, 2
and -28V at PCB04, P17 pin 8, 9
OK?
(Reconnect W8 after test)
Disconnect W6 from PCB35.1, P3.
Conrm +28V at PCB04, P15 pin 1, 2
and -28V at PCB04, P15 pin 8, 9
OK?
(Reconnect W6 after test)
Connect ServiceTool cable to
SERVICE connector.
Check connection between
PCB02.1, Input Panel and
PCB30, Digital Sound Engine
OK?
Repair/replace
connection
OK?
From
#1
Survey of plugs and pins - see page 2.11
*
Use ServiceTool to
autocalibrate the
new module

Fault ow chart 2.7
Fault symptom:
LED indicator is ashing quickly orange
(The product is in protection mode)
Possible causes:
Defective PCB30, Digital Sound Engine
Defective PCB35.1/2, Amplier
Defective PCB48.1/2/3, NTC Tweeter / Mid-
range / Woofer
Defective speaker unit
Disconnect product
from mains, wait 2
minutes and
reconnect to mains
OK?
No
**
Board temperature - PCB30, Digital Sound Engine
Power Supply temperature - PCB04, Power Supply
Amplier temperature - PCB35.1 and
PCB35.2, Amplier
Connect ServiceTool
and read out product ID.
Conrm all product ID data is correct
OK?
Read out the
temperature of the
tweeter **
Seems normal?
Measure the DC
resistance of the midrange (wires discon-
nected): Midrange = 6.2Ω ± 15%
OK?
Measure the DC
resistance of the woofer
(both terminal pair; wires disconnected):
Woofer = 6.0Ω ± 15%
OK?
Read out the
temperature **
Seems normal?
Read out Error Log
and follow
instructions
thoroughly
Make an
ID Restore.
Type in all product
ID data from the
product label
Yes
Replace the
suspected module
related to the high
temperature
*
Replace PCB30,
Digital Sound
Engine
*
Perform an
autocalibration
OK?
Replace defective
midrange
Use ServiceTool to
calibrate the new
speaker unit
Replace defective
woofer
Use ServiceTool to
calibrate the new
speaker unit
Disconnect the product from mains.
Disconnect PCB48.1/2/3, P1 on tweeter,
midrange and woofer and
conrm 470kΩ (at 22°C / 72°F)
at PCB48.1/2/3, NTC P1 pin 1-2
OK?
Replace defective
PCB48.1, NTC,
PCB48.2, NTC or
PCB48.3, NTC
Read out the
temperature of the
midrange **
Seems normal?
Read out the
temperature of the
woofer **
Seems normal?
Measure the DC
resistance of the tweeter (wires disconnected):
Tweeter = 6.7Ω ± 15%
OK?
Replace PCB35.1,
Amplier
*
Replace PCB35.2,
Amplier
*
Replace PCB35.1,
Amplier
*
Replace defective
tweeter
Use ServiceTool to
calibrate the new
speaker unit
Survey of plugs and pins - see page 2.11
*
Use ServiceTool to
autocalibrate the
new module

2.8 Fault ow chart
Survey of plugs and pins - see page 2.11
Replace PCB30,
Digital Sound
Engine
*
Fault symptom:
No sound from speaker in a wired setup
Possible causes:
Defective PCB04, Power Supply
Defective PCB30, Digital Sound Engine
Defective PCB35.1/2, Amplier
Incorrect role switch setting
Conrm that the
role switch setting
is correct
OK?
No
Set role switch
Conrm
+28V at PCB04,
P15 pin 1, 2 and
-28V at PCB04,
P15 pin 8, 9
OK?
Conrm
+28V at PCB04,
P16 pin 1, 2 and
-28V at PCB04,
P17 pin 8, 9
OK?
Yes
Check cables W2,
W9 and W10 and
connections to
speaker units and
PCB02.1, Input
Panel
Conrm
P15V = 15V at
PCB04, P14 pin 5
OK?
Conrm
PS_ON = 3.3V at
PCB04, P14 pin 7
OK?
Connnect to a
source via:
Power Link,
TOSLINK or line-in
signal
Replace PCB35.1,
Amplier
*
Replace PCB35.2,
Amplier
*
Replace PCB04,
Power Supply
Replace PCB30,
Digital Sound
Engine
*
Disconnect W6 from PCB35.1, P3.
Conrm +28V at PCB04, P15 pin 1, 2
and -28V at PCB04, P15 pin 8, 9
OK?
(Reconnect W6 after test)
Disconnect W8 from PCB35.2, P3.
Conrm +28V at PCB04, P17 pin 1, 2
and -28V at PCB04, P17 pin 8, 9
OK?
(Reconnect W8 after test)
Check connection
between PCB04,
Power Supply and
PCB30, Digital
Sound Engine
OK?
Repair/replace
connection
OK?
Connect ServiceTool and read out Error Log.
Replace the suspected module related to the
Error Log
OK?
Replace PCB04,
Power Supply
*
Use ServiceTool to
autocalibrate the
new module

Fault ow chart 2.9
Survey of plugs and pins - see page 2.11
Reset the speaker
and set up the
wireless connection
again
OK?
Replace PCB30,
Digital Sound
Engine
*
Fault symptom:
No sound from speaker in a wireless setup
Possible causes:
Defective PCB04, Power Supply
Defective PCB30, Digital Sound Engine
Defective PCB35.1/2, Amplier
Defective PCB89, Wireless Power Link Rx
Incorrect role switch setting
Conrm that the
role switch setting
is correct
OK?
No
Set role switch
Conrm
+28V at PCB04,
P15 pin 1, 2 and
-28V at PCB04,
P15 pin 8, 9
OK?
Conrm
+28V at PCB04,
P16 pin 1, 2 and
-28V at PCB04,
P17 pin 8, 9
OK?
Yes
Check cables W2,
W9 and W10 and
connections to
speaker units and
PCB02.1, Input
Panel
Conrm
P15V = 15V at
PCB04, P14 pin 5
OK?
Conrm
PS_ON = 3.3V at
PCB04, P14 pin 7
OK?
Connnect to a
source via:
Wireless
Replace PCB35.1,
Amplier
*
Replace PCB35.2,
Amplier
*
Replace PCB04,
Power Supply
Disconnect W6 from PCB35.1, P3.
Conrm +28V at PCB04, P15 pin 1, 2
and -28V at PCB04, P15 pin 8, 9
OK?
(Reconnect W6 after test)
Disconnect W8 from PCB35.2, P3.
Conrm +28V at PCB04, P17 pin 1, 2
and -28V at PCB04, P17 pin 8, 9
OK?
(Reconnect W8 after test)
Check connection
between PCB04,
Power Supply and
PCB30, Digital
Sound Engine
OK?
Repair/replace
connection
OK?
Connect ServiceTool and read out Error Log.
Replace the suspected module related to the
Error Log *
OK?
Replace PCB04,
Power Supply
Conrm
1V2 = 1.2V at
PCB89, P7 pin 22
and 3V3 = 3.3V at
PCB89, P7 pin 24
OK?
Replace PCB89,
Wireless Power
Link Rx
Replace PCB30,
Digital Sound
Engine
*
*
Use ServiceTool to
autocalibrate the
new module

2.10 Fault ow chart
Fault symptom:
Missing, atttenuated or distorted sound from
speaker and no error indication in error logs
Possible causes:
Defective PCB04, Power Supply
Defective PCB30, Digital Sound Engine
Defective PCB35.1/2, Amplier
Defective PCB89, Wireless Power Link Rx
Defective speaker unit
Check cables and
connections to all
speaker units
OK?
Distorted sound
from woofer
?
Reconnect or
replace cables
OK?
Replace PCB30,
Digital Sound
Engine
*
Conrm +28V at
PCB04, P17 pin
1, 2 and -28V at
PCB04, P4 pin 8, 9
OK?
Replace PCB04,
Power Supply
Replace PCB30,
Digital Sound
Engine
*
Conrm
PS_ON = 3.3V at
PCB04, P14 pin 7
OK?
Check connection
between PCB04,
Power Supply and
PCB30, Digital
Sound Engine
OK?
Repair/replace
connection
Conrm
1V2 = 1.2V at
PCB89, P7 pin 22
and 3V3 = 3.3V at
PCB89, P7 pin 24
OK?
Connect Service-
Tool and read out
Error Log
Any suggestions?
Replace PCB89,
Wireless Power
Link Rx
Replace the
suspected module
related to the
error log
*
Replace PCB30,
Digital Sound
Engine
*
Disconnect W8 from PCB35, P3.
Conrm +28V at PCB04, P17 pin 1, 2
and -28V at PCB04, P17 pin 8, 9
OK?
(Reconnect W8 after test)
Survey of plugs and pins - see page 2.11
Conrm +28V at
PCB04, P15 pin
1, 2 and -28V at
PCB04, P4 pin 8, 9
OK?
Replace PCB35.1,
Amplier
*
Replace PCB35.2,
Amplier
*
Disconnect W6 from PCB35.1, P3.
Conrm +28V at PCB04, P15 pin 1, 2
and -28V at PCB04, P15 pin 8, 9
OK?
(Reconnect W6 after test)
Go to
#3
Go to
#3
From
#3
If problem persists, check
PCB35.1 Amplier, PCB35.2 Amplier speaker
units and cables W2/W9.
Replace suspected modules or cables *
OK?
Make an autocali-
bration using the
ServiceTool.
Successful?
Check
PCB30, Digital Sound Engine, PCB35.1 Ampli-
er, PCB35.2 Amplier and cables W5/W7.
Replace suspected modules or cables
OK?
Go to
#2
From
#2
*
Use ServiceTool to
autocalibrate the
new module
No
Yes

2.112.11 Survey of plugs and pinsSurvey of plugs and pins 2.11
PCB04, Power Supply


N
L
IC
P13
ATTENTION
FTHV BT
©
4
LIVE PARTS
P17 P15
19 19
P14
18
+
+
+
+
++
++
+
−
+
++
+
+
+
+
P16
PCB48, NTC
P1
1
PCB35, Amplier
14
1
P2
P3
P1
81
11
224
8
PCB30, Digital Sound Engine
W356
33
49
17
P4
P3
P7
P1
P2
123
224
1 391
24
0
234
133
124
130
PCB02.1, Input Panel
Service
TOSLINK
IN
TOSLINK
OUT
TOSLINK
L
TOSLINK
R
POWER LINKPOWER LINK
P103P101P102
1
7
130124
PCB47, LED Indicator
P1
1
PCB02.2, Connector Interface
P2
1
P1 1
PCB68, Switch Panel
P1
1
2
PCB89, Wireless Power Link Rx
Solder side
Component side
Tweeter side
Cable side
BeoLab 20, Connection Panel and switches
FREE
WALL
CORNER
L
R
WL
ROLE POS.
RESET
POWER LINK R-INPUT-L IN-TOSLINK-OUT SERVICE

2.12 2.122.12

Adjustments - Final check after repair 3.1
Adjustments - Final check after repair
Adjustments
Information ...................................................................................... 3.2
PCB30, Digital Sound Engine ............................................................ 3.2
PCB35, Amplier .............................................................................. 3.3
PCB89, Wireless Power Link Rx ......................................................... 3.3
Connecting speaker wirelessly .......................................................... 3.4
Speaker units .................................................................................... 3.4
Software update ............................................................................... 3.5
Final check after repair
Insulation test ................................................................................... 3.6
Restore setup .................................................................................... 3.6
Software update ............................................................................... 3.6
Check sound .................................................................................... 3.6
Clean the product ............................................................................. 3.6

3.2 Adjustments
Adjustments
Information
Depending on the repair there might be different kinds of adjustments/alignment
to be performed, after maintenance of the product.
Some adjustments have to be done with the ServiceTool.
Adjustments or calibration is necessary when the following modules are replaced:
PCB30, Digital Sound Engine - when backup function is possible:
- Restore product data from the data backup
- Calibration of the amplier (done automatically)
PCB30, Digital Sound Engine - when backup function is not possible:
- Restore product data from factory data (ID Restore)
- Calibration of the amplier (done automatically)
PCB35, Amplifier:
- Calibration of the amplier
PCB89, Wireless Power Link Rx - when backup function is possible:
- Restore product data from the data backup
- Connecting speaker wirelessly
PCB89, Wireless Power Link Rx - when backup function is not possible:
- Order a pre-programmed PCB89, Wireless Power Link Rx
- Connecting speaker wirelessly
Speaker units:
- Calibration of speaker units
PCB30, Digital Sound Engine
Backup/Restore
This function is used when PCB30, Digital Sound Engine is replaced and it is still
possible to communicate with the old module. The following data is handled:
- ID number
- Serial number
- Type number
- Item number
- Calibration of speaker units
- Calibration of the amplier
- Product settings
- Wireless data
- A new calibration of the amplier is performed again.
Connect ServiceTool, launch BeoLab 20 and follow the procedure under Repair.