Transformer Thermal Protection; Fuses And Circuit Breakers; Controls; Filter Cleaning - Crown POWER-TECH 3 Reference Manual

The amplifier's fault protection system will put the
amplifier in drive protection mode in rare situations
where heavy common-mode current is detected in the
output. The unit should never output heavy common-
mode current unless its circuitry is damaged. Activating
drive protection helps prevent further damage.

3.3.4 Transformer Thermal Protection

All Power-Tech amplifiers have transformer thermal
protection. This protection circuitry is activated in
unusual situations where the unit's transformer
temperature rises to unsafe levels. Under these
abnormal conditions, the unit removes power to the high-
voltage transformer. The fan will continue to run in all
units except those with 220/240 VAC transformers. The
amplifier will return to normal after it cools to a safe
temperature.
It is very unlikely that your Power-Tech amplifier will ever
activate transformer thermal protection as long as it is
operated within rated conditions. Your amplifier is
designed to keep working under conditions where other
amplifiers would fail. But even when you exceed the
limits of a Power-Tech amplifier, it still protects itself—
and your investment—from damage.

3.3.5 Fuses and Circuit Breakers

Your amplifier's low-voltage power supply is protected
by an internal fuse, and its high-voltage power supplies
are protected by a circuit breaker. The circuit breaker is
built into the power switch for all Power-Tech 1 ,
Power-Tech 2 and 220/240 VAC Power-Tech 3
amplifiers. The circuit breaker is located on the back
panel of 100/120 VAC Power-Tech 3 amplifiers. With
rated loads and output levels, the circuit breaker will only
shut down the amplifier in the incredibly rare instance of
a catastrophic amplifier failure. Other protection systems
such as ODEP keep the amplifier operational under most
other severe conditions. The breaker can also shut down
the amplifier in situations where extremely low-
impedance loads and high output levels result in current
draw that exceeds the breaker rating. Again, this should
only be possible when operating outside rated
conditions , like when the amplifier is used to drive a 1
ohm load, or when driving a severely clipped signal.
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A Power-Tech amplifier will not blow its fuse or trip its
breaker unless something is wrong. In the rare event that
an internal fuse blows, please refer the unit to a qualified
technician. If a breaker trips, try to identify and correct
the problem before resetting the breaker. The breaker for
the Power-Tech 1 and 2 can be reset using the front
panel power switch. The circuit breaker for a Power-
Tech 3 can be reset using the back panel reset switch.
If the problem persists, refer the unit to a qualified
technician.

3.4 Controls

The power switch and level controls are located on the
front panel so you can easily turn the amplifier on or off
and adjust the amplifier's output level. When making any
setup or wiring changes, don't forget to turn the amplifier
off, turn the level controls down and disconnect the
power cord. The stereo/mono switch on the back panel
is used to select Stereo, Bridge-Mono or Parallel-Mono
operating modes. Be sure to leave Channel 2 turned
down when using either mono mode. The input
sensitivity switch located inside the back cover plate is
used to set the amplifier's input sensitivity (see Section
2.3 for information on changing this switch). And the
Power-Tech 3 has a back panel reset switch that is
used to reset the circuit breaker that protects the power
supplies.

3.5 Filter Cleaning

A dust filter is provided on the unit's air intake. If it
becomes clogged, the unit will cool less efficiently and
may produce lower output levels. To clean the filter, use
a Phillips screwdriver to remove the three screws that
secure the front grille. Use mild dishwashing detergent
and warm water for best cleaning results. Be sure the
filter is dry before you reinstall it. Replacement filters may
be ordered from the factory.
Dust filters are not 100% efficient—depending on the
local environment, the internal heat sinks of the amplifier
will benefit from periodic cleaning by a qualified
technician. Internal cleaning information is available
from our Technical Support Group.
Power-Tech Series Power Amplifiers
Reference Manual