Cooling; Protection Circuits - Lindemann 855 Owner's Manual

Cooling

The amount of heat generated by the 855 depends on how hard it is driven. It
is very important to ensure that there is unimpeded circulation of fresh air
from below and that hot air can escape behind and above the unit. When you
install your amplifier, therefore, make sure to provide adequate clearance
above and behind the unit. Make sure also that the location is protected
against direct sunlight. Operating the amplifier at room temperatures higher
than 30°C can lead to heat dissipation problems and is not recommended. The
855 is equipped with active cooling via a speed-controlled fan, which switches
on according to the ambient temperature and how hard the amplifier is
driven. At normal listening volumes, however, this is unlikely to happen.

Protection circuits

Intelligent protection circuits constantly ensure the proper functioning of the
855 amplifier. If a fault such as a DC, surge current or overtemperature fault
should occur, power to the electronics is immediately shut down to prevent
damage to the amplifier and speakers. A built-in inrush current limiter operates
at turn-on to protect the amplifier's components and prevent the mains circuit
breaker or fuse from tripping.
Overtemperature
Flashing yellow LEDs will warn you if the operating temperature becomes too
high while the amplifier is running. If you do not take steps to reduce the
output level, the amplifier will switch off and the fan will run at maximum
speed to cool the amplifier down to a safe temperature. While this is
happening, both yellow overtemperature LEDs illuminate continuously and
you will not be able to switch the 855 back on.
DC voltage
If an excessively high DC voltage is detected at the output, the 855 mutes the
signal and the red Fault LED illuminates. If the fault continues, the 855
disconnects the power to the amplifier. If this happens, the amplifier must be
switched off and restarted. However, if the amplifier will not restart, it has been
damaged and must be serviced!
Overcurrent
An over-current limiter protects the output stage of the 855 against excessive
current.
Power failure
A supply voltage sensor constantly monitors the mains supply voltage and
switches the unit off in the event of a power failure.
855 Dual Mono Power Amplifier
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