Crown 3, 2 Controls, Filter Cleaning, Transformer Thermal Protection, Fuses and Circuit Breakers

Power Base Series Power Amplifiers

The unit should never output heavy common-mode cur- rent unless its circuitry is damaged. Activating drive protection helps prevent further damage.

3.3.4 Transformer Thermal Protection

All Power Base amplifiers have transformer thermal protection. This protection circuitry is activated in un- usual situations where the unit’s transformer tempera- ture 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 ex- cept those with 220/240 VAC transformers. The ampli- fier will return to normal after it cools to a safe temperature.

It is very unlikely that your Power Base amplifier will ever activate transformer thermal protection as long as it is operated within rated conditions. Your amplifier is designed to continue operating under conditions where other amplifiers would fail. But even when you exceed the limits of a Power Base amplifier, it still pro- tects itself—and your investment—from damage.

3.3.5 Fuses and Circuit Breakers

All 120 VAC, 60 Hz units and all Power Base-3units have a fuse that protects the low-voltage power supply and cooling fan. The Power Base-1and Power Base-2high-voltage power supplies are protected by fuses, while the Power Base-3high-voltage power supplies are protected by a circuit breaker. With rated loads and output levels, these fuses (or the circuit breaker) should only shut down the amplifier in the incredibly rare instance of a catastrophic amplifier failure. The ODEP protection system keeps the amplifier opera- tional under most other severe conditions. The fuses (or breaker) can also shut down the amplifier in situa- tions where extremely low-impedance loads and high output levels result in excessive current draw.

A Power Base amplifier will not blow its fuses 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 the breaker in a Power Base-3trips, try to identify and correct the problem before re- setting it with the back panel Circuit Breaker Reset. If the problem persists, refer the unit to a qualified techni- cian.

3.4 Controls

The Power switch is th only control located on the front panel. All others are located on the rear, including the level controls.

When making any setup or wiring changes, don’t forget to turn off the amplifier, turn down the level controls and disconnect the power cord. Be sure to turn down (full counterclockwise) the channel 2 level control when us- ing either mono mode. The Parallell Mono/Stereo/ Bridge Mono switch is used to select Stereo, Bridge- Mono or Parallel-Mono operating modes. The Input Ground Lift switch isolates the phone jack input grounds from the chassis ground to help prevent ground loops. It does not affect any installed input ac- cessories. The Input Sensitivity Switch, located inside the back cover plate, sets the amplifier’s input sensitiv- ity (refer to subsection 2.3 for information on changing this switch). And the Power Base-3has a back panel Circuit Breaker Reset button that resets the circuit breaker (refer to subsection 3.3.5).

CHANNEL 2	CHANNEL 1
LEVEL CONTROL	LEVEL CONTROL

	6		CH-2				CH-1	6
5		7					5		7
4			8				4		8
3			9				3		9
2			10		INPUT GROUND LIFT		2		10
1			11				1		11
0		12		INPUT	LIFT	INPUT	0		12
GAIN							GAIN
					(AFFECTS PHONE INPUTS ONLY.)	(MONO)

Fig. 3.1 Back Panel Level Controls

3.5 Filter Cleaning

A dust filter is provided on the unit’s air intake. If it be- comes 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 the secure the front grille. Use mild dishwashing deter- gent and warm water for best cleaning results. Be sure the filter is dry before you reinstall it. Replacement fil- ters may be ordered from the factory.

Dust filters are not 100% efficient—long term this may require internal heat-sink cleaning by a qualified tech- nician. Internal cleaning information is available from our Technical Support Group.

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