Bang & Olufsen BeoLab 20, Service Manual, Page: 13 / 68

Fault flow chart 2.7
Fault symptom:
LED indicator is flashing quickly orange
(The product is in protection mode)
Possible causes:
Defective PCB30, Digital Sound Engine
Defective PCB35.1/2, Amplifier
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
Amplifier temperature - PCB35.1 and
PCB35.2, Amplifier
Connect ServiceTool
and read out product ID.
Confirm 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
confirm 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,
Amplifier
*
Replace PCB35.2,
Amplifier
*
Replace PCB35.1,
Amplifier
*
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