Altec Lansing 1270 User's Manual
Contents
1. ALTEC LANSING CAUTION 1270 POWER AMPLIFIER OPERATING INSTRUCTIONS No user serviceable parts inside Hazardous voltage may be en countered within the chassis Installation and Service information within this document is for use only by ALTEC sound contractors factory authorized warranty stations and qualified service personnel IMPORTANT Il est enjoint l utilisateur de ne pas r parer lui m me les pieces internes de l appareil des courants a haute tension pouvant pas ser l int rieur du chassis Les renseignements inclus dans ce document sont destin s uniquement l usage des installateurs agr s des syst mes acoustiques ALTEC des centres de r paration sous garantie autoris s ainsi que du personnel d entretien qualifi INTRODUCTION The ALTEC LANSING Model 1270 Power Amplifier provides continuous high power demand where uninterrupted operation is requisite Designed to protect itself and the acoustic elements it drives the Model 1270 represents 800 watts of controlled power Two channels may be operated independ ently in parallel or in bridged configuration to deliver up to 400 watts per channel at less than 0 05 THD from 20 Hz to 20 KHz Peak Error Computer The amplifier is provided with a peak error computer that compares channel input and output signals and detects any output errors Detection of any peak error causes the appropriate peak error indicator to illu2. c ID Q v lt T 3a Independent Operation of L and R Channels OUTPUT Te NOT CONNECTED NOT CONNECTED 00 Qo eo CAUTION Bridged operaton provides a true bal anced output Do not connect either side of the loudspeaker line to audio common or to any other ground connection 3b Bridge Operation of L and R Channels Figure 3 Output Connections STEREO INDEPENDENT CHANNEL OPERATION T After installation and hookup of connec tions as in Figure 3A check that the BRIDGE NORMAL switch is positioned at NORMAL and that the LEFT and RIGHT CHANNEL volume controls are turned fully counterclockwise Set input signal level to the 1270 at a nominal value of 0 775V Turn on ac line POWER switch and note illumination of POWER indicator 4 Turn LEFT and RIGHT CHANNEL vol ume controls clockwise until desired output power is obtained If either LEFT or RIGHT peak error indicator illumi nates reduce output level with channel volume control or reduce input level to 1270 BRIDGE MONO OPERATION 1 After installation and hookup of connec tions as in Figure 3B check that the BRIDGE NORMAL switch is positioned at BRIDGE and that the LEFT and RIGHT CHANNEL volume controls are turned fully counterclockwise o Set input signal level to the left L INPUT of the 1270 at a nominal value of 0 775V The right R INPUT is left unconnected 3 4 Turn on ac line POWER switch and n
3. to qualified service per sonnel if fuse blows repeatedly Balanced input connections are made with the optional 1270TM Dual Balanced Trans former Input Module Plug the 1270TM into the INPUT receptacles of the 1270 and secure the retaining screw See Figure 1 Cables terminated with XLR3 type connec tors are used to make input connections to the 1270 TM module wiring for the XLR8 type connector is shown in Figure 2 SECURING SCREW MODULE JACKS DAUT vee CHANNEL INPUT RECEPTACLES 1b Module Installed Figure 1 Installation of 1270TM Module Figure 2 Wiring for XLR3 type Connector Line Out Connections Connections to LINE OUT receptacles are made with shielded single conductor cables terminated with standard 14 inch phone jacks When channels are operated independently stereo operation a cable must connect each channel of each addi tional 1270 amplifier connected in multiple When channels are operated in the bridge mode only the left channel of each addi tional 1270 requires a connecting cable Output Connections Output connections are made at the L and R OUTPUT terminals Figure 3 illustrates connections for independent stereo opera tion and for bridged operation GND and COM Connections The GND chassis ground and COM elec trical common terminals are used to cor rect unsatisfactory grounding conditions and for establishing desired grounding configurations OUTPUT R
4. er cord Verify that line voltage is in accordance with specified volt age before connecting the 1270 to ac line power 100V 200V 220V 240V 50 60 Hz Power Connections Refer to Authorized Altec Service Representative Input Connections Unbalanced input connections to the INPUT jacks are made with shielded single conductor cables terminated with standard Ya inch phone jacks In preparing the cable the conductor is soldered to the tip of the jack and the shield is soldered to the sleeve item Name Function Description OUTPUT Terminals INPUT Receptacles LINE Receptacles BRIDGE NORMAL Switch COM Terminal GND Terminal FAN Switch Fuse Connect left L and right R channels to corresponding speak ers Two pair of standard GR jacks have red and black polarity designations Accept cables from high impedance nominal 15 000 ohms sources Use standard ring and sleeve plug for left L and right r receptacles Accept cables to connect other Altec Amplifiers in parallel Use standard ring and sleeve plug for left L and right R receptacles Connects internal circuitry for independent or mono operation NORMAL into a 4 ohm load of bridge operation BRIDGE into 8 ohms Provides connection to circuit common Provides connection to chassis ground Selects low 1 or high 2 fan speed Protects amplifier from excessive current drain Replace only with same type 10 ampere fuse Refer
5. minate Output anomalies detected include excessive voltage excessive current load excessive slew rate and any other signifi cant difference between the channel input and output signal Amplifier Protection The amplifier output is continuously mon itored to guard against excessive current drain An instantaneous VI limiter restricts output to 400 VA 45 phase shift The amplifier is additionally protected against excessive operating temperature logic cir cuitry automatically overrides low speed fan operation and locks to the high fan speed mode If operating temperature remains excessive the load is discon nected by a relay and the protection indica tor illuminates When temperature falls to safe operating conditions the amplifier automatically resumes operation ALES notice Load Protection The load is protected from transients dur ing startup and shutdown of the amplifier During startup the load remains discon nected through a relay during a three FRONT PANEL CONTROLS AND FEATURES second delay period During shutdown or loss of power the load is instantaneously disconnected by the relay The load is simi larly protected against amplifier failure such as dc voltage at the output item Name Function Description Peak Error Indicators Protection Indicator POWER Indicator Illuminate when excessive voltage current or slew rate ap pears at the output terminals illuminates when pro
6. ote illumination of POWER indicator Turn LEFT CHANNEL volume control clockwise until desired output power is obtained Be sure to leave RIGHT CHAN NEL volume control fully counterclock wise If LEFT peak error indicator illu minates reduce output level with LEFT CHANNEL volume control or reduce input level to the 1270
7. tection circuitry operates to prevent dam age to the amplifier or load Illuminated when primary ac power is applied to the amplifier POWER Switch Applies primary ac power to the amplifier CHANNEL Volume Controls increase gain Specifications and components subject to change without Overall performance will be maintained or improved 1515S Manchester Ave Anaheim Calif 92803 Adjust gain of LEFT and RIGHT channels Rotate clockwise to 42 02 045589 01 LITHO IN U S A 681 1M INSTALLATION Rack Mounting The 1270 may be installed in a standard 19 inch equipment rack or in the 42526 Shelf Mount Cover Accessory for shelf use Vertical space required is 5 Rack instal lation is accomplished by using the appro priate four mounting screws supplied Ventilation The 1270 must be adequately ventilated to prevent excessive temperature rise Max imum rated ambient operating temperature is 55 C 131 F CAUTION Do not block the side ventilation aperatures on either side of the main frame Allow at least 2 on each side of the main frame to assure adequate ventilation Do not operate within a completely closed unventilated housing REAR PANEL CONTROLS AND FEATURES ELECTRICAL 120 Volt 50 60 Hz Power Connections Equipment supplied for domestic use is provided with the power transformer primary strapped for 120 volts Specified voltage rating is located on the chassis adjacent to the pow
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