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1、 1998 Bose Corporation Service Manual RadioFans.CN 2 PROPRIETARY INFORMATION THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF BOSE CORPORATION WHICH IS BEING FURNISHED ONLY FOR THE PURPOSE OF SERVICING THE IDENTIFIED BOSE PRODUCT BY AN AUTHORIZED BOSE SERVICE CENTER OR OWNER OF THE BOSE PRODUCT, AN
2、D SHALL NOT BE REPRODUCED OR USED FOR ANY OTHER PURPOSE. Contents Safety Information. 3 Specifications. 4 Technical Description . 5-6 Figure 1. Equalizer Controls Response Charts. 6 Disassemble/Assembly Procedure .7-8 Figure 2. Staple Location . 7 Figure 3. Staple Removal Tool . 7 Figure 4. Wiring D
3、iagram . 7 Figure 5. Top Cover. 9 Figure 6. Front Panel Assembly . 9 Figure 7. Indicator Lens Assembly . 9 Test Procedure . 10-11 Figure 8. Test Set-Up . 10 Part List. 12 Part List Notes. 12 Figure 9. 901 I Schematic Diagram. 13 Figure 10. 901 II Schematic Diagram. 14 Figure 11. 901 Schematic Diagra
4、m (first production run). 15 RadioFans.CN 3 CAUTION: THE BOSE 901 I and II EQUALIZERS CONTAIN NO USER-SERVICEABLE PARTS. TO PREVENT WARRANTY INFRACTIONS, REFER SERVICE TO WARRANTY SERVICE STATIONS OR FACTORY SERVICE. SAFETY INFORMATION 1. Parts that have special safety characteristics are identified
5、 by the symbol on schematics or by special notes on the parts list. Use only replacement parts that have critical characteristics recommended by the manufacturer. 2. Make leakage current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit befor
6、e returning the unit to the customer. Use the following checks to perform these measurements: A. Leakage Current Hot Check-With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. (Do not use an isolation transformer during this test.) Use a leakage current tester
7、or a metering system that complies with American National Standards Institute (ANSI) C101.1 “Leakage Current for Appliances” and Underwriters Laboratories (UL) 1492 (71). With the unit AC switch first in the ON position, then in the OFF position, measure from a known earth ground (metal water pipe,
8、conduit, etc.) to all exposed metal parts of the unit (antennas, handle bracket, metal cabinet, screw heads, metallic overlays, control shafts, etc.), especially any exposed metal parts that offer an electrical return path to the chassis. Any current measured must not exceed 0.5 milliamp. Reverse th
9、e unit power cord plug in the outlet and repeat test. ANY MEASUREMENTS NOT WITHIN THE LIMITS SPECIFIED HEREIN INDICATE A POTENTIAL SHOCK HAZ- ARD THAT MUST BE ELIMINATED BEFORE RETURNING THE UNIT TO THE CUSTOMER. B. Insulation Resistance Test Cold Check-(1) Unplug the power supply and connect a jump
10、er wire between the two prongs of the plug. (2) Turn on the power switch of the unit. (3) Measure the resistance with an ohmmeter be- tween the jumpered AC plug and each exposed metallic cabinet part on the unit. When the exposed metallic part has a return path to the chassis, the reading should be
11、between 1 and 5.2 Megohms. When there is no return path to the chassis, the reading must be “infinite”. If it is not within the limits specified, there is the possibility of a shock hazard, and the unit must be repaired and re- checked before it is returned to the customer. RadioFans.CN 4 SPECIFICAT
12、IONS 901 Series I and II Speaker Dimensions:20-9/16 W x 12-3/4 H x 12-7/8 D Weight:33 lbs Nominal Impedance:8 ohms Percentages of Direct and Reflected Sound Radiation Power radiated by reflection:89% Power radiated directly:11% Power Handling:Continuous sine wave any frequency:50 Watts Minimum ampli
13、fier power:25 Watts Peak power (less than 5 seconds):400 Watts Maximum amplifier power:270 Watts rms 8 ohms Damping Factor:Any amplifier with a damping factor of 40 or higher (must follow the speaker wire recommendation in the Owners Guide) Driver Complement:Nominal driver diameter:4-1/2 Maximum dri
14、ver excursion: 1/4 Nominal driver impedance:8 ohms Weight of each ceramic magnet:9.6 ounces 901 Active Equalizer Dimensions:2-13/16 H x 9-1/4 W x 6-3/4 D Input Impedance:150k ohms Output Impedance:Less than 100 ohms Minimum Load Impedance:5k ohms Maximum Output Voltage:4.0 Volts Maximum Gain:18 dB 3
15、5 Hz RadioFans.CN 5 TECHNICAL DESCRIPTION The Bose 901 speakers represent a fundamental advance in realistic home music reproduc- tion. The unique acoustic design of the speakers provide sound distribution in accurate simula- tion of live sound. The Active Equalizer provides unprecedented accuracy a
16、nd control of frequency response characteristics. Each speaker contains nine high compliance, full range speakers with high energy magnets to allow large excursions without audible distortion on any program material. The speakers are acoustically coupled to eliminate audible resonances. The 901 spea
17、kers can be used with any high quality amplifier. Its efficiency enables operation with moderately powered amplifiers, yet it can be used with the highest powered amplifiers to reproduce undistorted orchestral peaks at high volume levels. The Bose 901 Active Equalizer is a highly sophisticated elect
18、ronic console containing ten transistors and more than a hundred components to equalize accurately the stereo response for the effects of radiation impedances, speaker characteristics, enclosure dimensions and even for the presence of the fashion fabric grille cloth. This equalization to flat power
19、radiation is achieved with absolutely no audible distortion of any music or speech signals. Active equalization of the signal before the power amplifier is far superior to passive equaliza- tion after the amplifier because it avoids the need to handle high power and does not require the iron-core in
20、ductors that introduce distortion in passive equalizers. In addition, it is feasible to use many more elements in an active network to provide much greater accuracy in equaliza- tion than is practical in the passive network. The Active Equalizer does much more than just equalize. In addition to prov
21、iding the flat acoustic output of the Bose 901, the Active Equalizer offers the choice of nineteen additional contours that can be selected from the front panel. This gives the listener the flexibility to exercise his own taste in compensating for recording techniques, listening room characteristics
22、 and the other variables described above. As an example of what is possible through active equalization, the equalizer panel contains a switch marked BELOW 40, which reduces turntable rumble and other low frequency disturbances through a unique filter design that provides a uniform attenuation below
23、 40 Hz while causing no audible deviations above 50 Hz. The rumble is removed without removing the life of the bass along with it. RadioFans.CN 6 TECHNICAL DESCRIPTION Figure 1. Equalizer Controls Response Charts RadioFans.CN DISASSEMBLE/ASSEMBLY PROCEDURE 901 Speaker Disassembly/Assembly 1. Grille
24、Removal 1.1 Locate the staples that secure the front or rear grille assembly. Refer to Figures 2 and 3 for the staple placement and tool for removing the staples. 1.2 When removing the front grille assem- bly, note the placement of the cut out in the grille backing. 2. Grille Replacement 2.1 Place t
25、he front grille assembly over the front of the speaker. Note the cut out in the grille backing, be sure to align the cut out with the driver ( on late versions the front grille assembly had two cut outs so the grille placement would not be a factor when reassembling the speaker). Secure using new st
26、aples or small finishing nails. 2.2 Place the rear grille assembly on to the speaker and secure using new staples or small finishing nails. 3. Driver Removal 3.1 Perform procedure 1. 3.2 Remove the screws that secure the defective driver. 3.3 Lift the driver out of the cabinet and cut the speaker wi
27、re as close to the driver terminals as possible. 4. Driver Replacement 4.1 Connect the speaker wires to the new driver. Refer to Figure 4 for the wire dia- gram. 4.2 Place the new driver and gasket into the cabinet and secure it in place. 4.3 Perform procedure 2. Figure 2. Staple Location Figure 3.
28、Staple Removal Tool Figure 4. Wiring Diagram Flat Blade Screwdriver Machined to a Hook 7 RadioFans.CN 8 DISASSEMBLE/ASSEMBLY PROCEDURE 901 EQ Disassembly/Assembly 5. PCB Removal 5.1 Perform procedure 1. 5.2 Remove the four screws that secure the PCB to the chassis and lift the PCB out. 6. PCB Replac
29、ement 6.1 Place the PCB into the chassis and secure it to the chassis. 6.2 Perform procedure 2. 7. Treble Control Removal 7.1 Perform procedure 3. 7.2 Remove the wires form the control, make note of the placement of the wires. 8. Treble Control Replacement 8.1 Solder the wires onto the control. 8.2
30、Place the control into the chassis and secure it in place. 8.3 Perform procedure 4. 9. Switch Removal 9.1 Perform procedure 3. 9.2 Remove the wires from the switch, make note of the placement of the wires. 9.3 Remove the rivets that secure the switch to the chassis, using a drill. 10. Switch Replace
31、ment 10.1 Secure the new switch to the chassis using rivets or screws. 10.2 Solder the wires to the switch. 10.3 Perform procedure 4. Note: Refer to figures 5 and 6 for the following procedures. 1. Top Cover Removal 1.1 Turn the unit over (top down) and remove the four screws located at each of the
32、corners. 1.2 Flip the unit back over and remove the top cover. 2. Top Cover Replacement 2.1 Align the top cover with the front panel (there is a groove in the top cover for the front panel to slide into). 2.2 Flip the unit over and secure the top cover using the screws that had been removed. 3. Fron
33、t Panel Removal Note: The series II EQ has a red indicator lens. Refer to Figure 7. for removal. 3.1 Perform procedure 1. 3.2 Remove the treble control knob using an Allen Wrench to loosen the set screw. 3.3 Remove the nut holding the treble control to the chassis. 3.4 Remove the small nut on the in
34、side of the chassis that secures the front panel to the chassis. 4. Front Panel Replacement 4.1 Align the front panel screw with the chassis. 4.2 Secure the front panel to the chassis. 4.3 Secure the treble control to the chassis and replace the control knob. 4.4 Perform procedure 2. RadioFans.CN 9
35、901 I EQ 901 II EQ Figure 5. Top CoverFigure 6. Front Panel Assembly Figure 7. Indicator Lens Assembly RadioFans.CN 10 TEST PROCEDURE 1. Rub and Tick Test 1.1 Apply a 10 Hz, 25 Volts rms signal (with the use of an amplifier) to the speaker terminals. Refer to Figure 8. No extraneous noises such as r
36、ubbing, scraping, or ticking should be heard. 2. Sweep Test 2.1 Apply a 25 Volt signal, and slowly sweep the oscillator from 10 Hz to 75 Hz. There should be no loud extraneous noises. If there are any loud buzzes or distortion, replace any defective driver. 2.2 Reduce the amplifier output to 10 Volt
37、s and continue sweeping the signal from 75 Hz to 15 kHz. Listen for any buzzes, rattles, and other extraneous noises. Dress any wires that might be the cause of the noise. 3. Phase Test 3.1 Using a 6 to 12 Volt dc supply. Connect the positive (+) wire to the positive terminal and the negative (-) wi
38、re to the negative terminal on the speaker. Check that all drives are in phase, all drivers should move outward. If one or more drivers move inward the wiring should be checked. Refer to Figure 4. Figure 8. Test Set-Up 901 I and II speaker Test 901 I and II Equalizer Test 1. Gain Test Note: The swit
39、ches should be pushed in at the top and the treble contour rotary switch should be on the dot. 1.1 Apply a 200 Hz, 500 mV signal to the input. 1.2 Reference a dB meter to the input signal applied. 1.3 Increase the input voltage to 4.25 Volts for the series I EQ and 5 Volts for the series II. The res
40、ponse should be 18 dB for the series I, and 19 dB for the series II 3 dB. 2. Frequency Response Test 2.1 Apply a 200 Hz, 500 mV signal to the input. 2.2 Reference a dB meter to the output. 2.3 Refer to the frequency response table on the following page for the response test. RadioFans.CN 11 TEST PRO
41、CEDURE Frequency Response Table FrequencyBelow 40 Switch Treble Decrease Switch Treble Contour Response dB 901 I Response dB 901 II Tolerance dB 20 HzOFFOFFnormal (dot)14.8 dB19 dB3 dB 20 HzONOFFnormal (dot)9 dB9.5 dB3 dB 60 HzOFFOFFnormal (dot)9.2 dB9.4 dB3 dB 60 HzON OFFnormal (dot)8 dB7.8 dB3 dB
42、1 kHzOFFOFFnormal (dot).2 dB.1 dB3 dB 5 kHzOFFOFFnormal (dot)2.2 dB4 dB3 dB 12 kHzOFFOFFnormal (dot)9 dB12.3 dB3 dB 12 kHzOFFONnormal (dot)6.9 dB8.1 dB3 dB 12 kHzOFFOFFnumber 12.7 dB7 dB3 dB 12 kHzOFFOFFnumber 23.2 dB7.8 dB3 dB 12 kHzOFFOFFnumber 37.3 dB-3 dB 12 kHzOFFOFFnumber 4-15.6 dB3 dB 12 kHzO
43、FFOFFnumber 512.4 dB18.5 dB3 dB 20 kHzOFFOFFnormal (dot)12.9 dB13.8 dB3 dB RadioFans.CN 12 PART LIST 901 Speaker Part List Item Number DescriptionPart Number Note -Driver1033424 -Grille, Front103514-034 -Grille, Rear103512-034 -Grille, Front , Ebony103514-024 -Knurled Nut100424-1 -Fuse Kit (External)1089
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