Bang & Olufsen Beoplay A9 3rd Generation, Руководство по обслуживанию

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2.6 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 Nominal value Limits
Tweeter 4.9 ohm 4.4 - 5.5 ohm
Midrange 3.5 ohm 3.1 - 3.9 ohm
Full Range 3.0 ohm 2.6 - 3.4 ohm
Woofer 2.0 ohm 1.7 - 2.3 ohm
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.
NTC module test
Measure the resistance of the NTC module to determine if the fault is caused by a
defective speaker unit or a defective NTC module.
It is recommended to measure on the terminals on the NTC module.
The NTC module must be disconnected from the product.
The resistance of the NTC module at 22ºC (72ºF) is approximately 470k ohm.
If the NTC module is not measuring approximately 470k ohm, it is defective and
must be replaced
Mechanical cracking sound(s)
We have heard cracking sounds from the cabinet of some products. Both when
the product is in use and also in standby after use. These mechanical cracking
sounds are caused by temperature deviations, and they can occur very periodically.
Work-around:
Switch on the product and when it is heated up, loosen all screws on the front of
the product. When all screws are loose, retighten like on a car wheel by always
crossing to the opposite side until all screws are tightened. See page 4.3 for
instructions on the order in which the screws must be tightened.