Altec Lansing 6125A Specific conditions resulting in a fault are as follows, Typical Applications

Operating Manual 6125A and 4200A Multi-Channel Power Amplifier

In all cases, the amplifier will restart the signal processing module after a short delay and will reconnect the speakers after several seconds if no further fault con- ditions exist. This allows the servo circuitry to bring any residual DC offsets to zero before speakers are connected.

Specific conditions resulting in a fault are as follows:

8.1Power supply undervoltage - less than about 55 volts on the either supply rail. Possible causes would

be total load on the outputs exceeding recommendations (remove some speakers - 4Ω load min, 8Ω min bridged),

low AC mains voltage (reduce extension cord length or increase wire size, or switch to an AC mains circuit more capable of supporting the amplifier's power requirements), or improper AC inlet mains voltage setting (make sure nominal AC mains voltage matches the number in the view- ing window on the AC inlet).

8.2Power supply overvoltage - more than about 92 volts on either supply rail. Possible causes would be high AC mains voltage (change to an AC mains circuit with voltage within the amplifier's stated requirements) or im- proper AC inlet mains voltage setting (make sure nominal AC mains voltage matches the number in the viewing win- dow on the AC inlet).

8.3Output overcurrent - more than 15 to 20 amps being drawn from any output. Possible causes would be total load on the affected output exceeding recommenda- tions (disconnect some speakers), or a short circuit on one of the outputs driven by the affected module (inspect speaker wiring for proper connection).

The above conditions are checked by the signal processing module on a switching cycle by switching cycle basis and are therefore monitored as often as a million or more times a second, allowing protection well before de- structive conditions have time to cause part failure.

8.4Heat sink overtemperature - a measured heat sink extrusion temperature of more than 85 to 90 degrees C. The three-speed fan will switch to medium speed at an extrusion temperature of 45 to 50 degrees C, and to high speed at a temperature of 70 to 75 degrees C. The overtemperature fault will clear itself when the measured temperature is below about 70 degrees C. The fan will operate at low speed below about 50 degrees C.

8.5Unacceptable DC or high frequency output content - a DC offset in the output signal of more than a few hundred millivolts indicates module failure, and will trigger a DC protect fault. High frequency (20kHz to 100kHz) in the output at high amplitudes can cause speaker damage and causes a fault condition more or less rapidly as frequency and amplitude vary.

These two conditions (DC and HF) are tested by the same circuit so the exact cause cannot be isolated. If the fault condition persists after disconnecting all inputs and outputs from the amplifier, there is probably a module failure requiring service. Note: the self-testing circuit may take as long as 30 seconds to recover from this fault, so be sure to give the amplifier enough time to reset itself. If after 30 seconds the module has recovered, begin plug- ging in one input and output at a time in an effort to iso- late a system high-frequency or oscillation problem.

8.6AC power interruption - a dropout (or brown- out of sufficient magnitude) of more than one half mains line cycle and less than one whole cycle in duration.

9.TYPICAL APPLICATIONS

The 6125A is essentially three stereo amplifiers in one chassis, each with dual stereo, dual mono, and bridged mono capabilities, while the 4200A is two stereo amplifiers (four channels), but with more power per chan- nel than the 6125A. Input connections are hard-wired with two-piece Euroblock connectors, while speaker outputs are wired to four position screw terminal blocks. Note: The 6125A is used for the following application details, but the 4200A is used in a similar fashion, to a maximum of four channels.

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