Bang Olufsen Beolab 4 Service Manual

BeoLab 4

Type 6650, 6652

Service Manual
English

German, French, Italian, Spanish, Danish, Dutch and Japanese versions
are available in the Retail System

This Service Manual must be returned with the
defective parts/back-up suitcase !

CONTENTS

Survey of modules ...................................................................... 1.1

How to service ......................................................................... 1.2

Warnings – Insulating test ........................................................ 2.1

Adjustments ............................................................................ 3.1

Repair tips ................................................................................ 4.1

Disassembly ............................................................................. 5.1

Specification guidelines for service use .....................................

6.1

Block diagram ........................................................................... 7.1

Wiring diagram ........................................................................ 7.2

Available parts ......................................................................... 8.1

1.1Survey of modules

PCB1 Amplifier

PCB2 SMPS

PCB3 Filter

PCB4 LED

PCB5 Switch

PCB6 Input

Survey of modules

4

5
6

1
2

3

How to service

1.2

How to service

Front line service

BeoLab 4 is to be serviced in the customer’s home when it comes to electrical
symptoms or exchange of mechanical parts. In this way you avoid having to make
more than one visit and using minimum of time on the case, all for the benefit of
the customer.
BeoLab 4 has been split-up into as few service items as possible. Each service friendly
item is packed individually, prepared for worldwide transport, and has a separate
seven digit spare part number to be found in the Bang & Olufsen Retail System or
the Service Manual. The exploded view drawing will show the service spare parts.

Back-up suitcase

A back-up suitcase contains all necessary electrical modules for front-line repair of
one loudspeaker. Cabinet parts must be ordered separately in the Retail System or
directly from B&O Struer DK.
The replaced modules must be returned for repair at Bang & Olufsen, Module
Repair Department. Use the Module Repair form or the form in the Retail Order
System, Exchange Module.

Delivery

As there is only one type number for BeoLab 4, the product can be used for all
markets with 100 to 240 Vac mains voltage. When you order BeoLab 4 (set of
two) this includes two mains cables, two Power Link cables and two boxes with
the three front covers in the chosen colour. This means that the delivery will
consist of four boxes.
This setup allows our packaging department to pack the specific order for the
customer no matter which country it goes to or the colour chosen.

Installation and setting-up

Only the switch for loudspeaker placement and the switch for Left or Right - Line
or PC must be set into correct position as described in the User Guide before
Power Link/Line signal and AC power wires are connected. If the Power Link is
used, the switch is for Left or Right setting. If Line connection is used (via mini-jack
plug) the switch is for Line (0 to 1V) or PC-line (0 to 2V) setting. See more details
in the User Guide. The automatic switch-off circuit is only active with the switch in
Line position, and is not active with the switch in PC-line position.
The LED will indicate on (green) or off (red) only.

Fault Finding

Before troubleshooting is initiated, let the customer demonstrate the fault, if possible.
There are four electrical modules in the product, and furthermore two additional
modules. One with a LED and one with a mini jack socket. Therefore a faulty module
is easy to point out in most cases. The PCB’s has been divided into the functionality:
Inputs, Amplifier, Power supply and Filter.
No special service programs are available in this product or via the ServiceTool.
If there is a fault in the SMPS (PCB2) or Amplifier (PCB1) the LED is typically off.
Only the tweeter unit is protected by a circuit that measures the resistance in the coil,
and will automatically turn down the signal level for the tweeter shortly if it is too
high for a period.

How to service 1.3

Replacement

Replacement of a loudspeaker unit or the amplifier.
Each loudspeaker is individually adjusted from production to secure optimal stereo
perspective.
If a defective loudspeaker unit must be replaced, it is easily done without adjustment
due to the specifications of the unit.

Mechanics

All cabinet parts as e.g. the socket panel can be changed on-site. All surfaces can
be cleaned with a mild detergent.
Internal parts are supplied as service kits, e.g. the loudspeakers, PCB’s etc.
A product cover (soft) for service, black, can be ordered for transport of BeoLab 4.

2.1 Warnings – Insulating test

Warnings

ESD

When electrical replacements or disassembly is taking place, use an ESD-mat. The
internal electronics are very sensitive to static electricity.

Handling

Wear cotton gloves to avoid any fingerprints on the product.

The surfaces on the product are very sensitive, so handling should be done with
great care to avoid damage.

Cleaning of the speaker surfaces should only be done with a lint-free cloth which
you have dipped in lukewarm water and wrung firmly.

Insulation test

The product must be insulation tested after having been dismantled. Make the test
when the set has been reassembled and is ready to be returned to the customer.
Flashover must not occur during the test.

Make the insulation test as follows:
Short-circuit the two pins of the mains plug and connect them to one of the
terminals of the insulation tester.
Connect the other terminal to ground on the Power Link socket.

NOTE!
To avoid damaging the product it is essential that both terminals of the insulation
tester have good contact.

During the test the current must not exceed 5 mA.
Slowly increase the voltage on the insulation tester until a voltage of 2.5 kV (ac) is
obtained. Maintain the voltage level for one second, then slowly decrease the
voltage to 0 V (ac).

STATIC ELECTRICITY
MAY DESTROY THE
PRODUCT

Adjustments 3.1

Adjustments

Adjustments after replacing PCB3 or PCB5

Read out the adjustment position of the old potentiometers, VR601 & VR701, and
set the new potentiometers to the same position.

PCB3 – VR601

PCB5 – VR701

VR601

VR701

4.1 Repair tips

Repair tips

Hum in loudspeaker when no music is played.
The Power Link cable must be of type MK III or higher.
The ground connection in Power Link cable lower than MK III may be insufficient
for optimum sound performance.
The loudspeaker units can be checked by an ohm-meter (tweeter 5.7Ω ±10%;
woofer 6.7Ω ±10%).

Power Link

MK III

Disassembly 5.1

- Pull off front covers

Remove front cover