Free Audio Service Manuals - Free download bose 901 iii spk service manual

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Figure 1 Speaker Schematic Figure 2 Driver Placement (Rear View)

DISASSEMBLY PROCEDURE

REMOVING THE REAR GRILLE - The rear grille assembly is secured in10 locaions with double-sided tape. (See Figure 4). This tape is
designed to allow grille panel removal once or twice. Carefully lift the panels out, starting at the V of the speaker cabinet taking care not to
scratch the air columns. The rear panels can be reattached using the doublesided tape.

Additional tape (Bose P/N 108645) can be ordered if necessary.

. REMOVING THE FRONT GRILLE - The front grille of the 901 Series III speaker system is secured by staples located in six positons along the

front grille. (See Figure 3). Remove the staples and lift the grille panel away from the cabinet assembly. The grille panels can be reattached using
colored finishing nails.

TEST PROCEDURE

. CONTINUITY CHECK - An open driver may be detected by using an ohmmeter and checking continuity. Carefully penetrate the black

cement covering the flexible conductor on the surface of each cone with the ohmmeter lead. Check continuity between each driver and the
speaker terminals until the open driver is detected. (See Figures 1 and 2).

POWER CHECK - Using a 50 watt (20 volt) sine wave signal. sweep the range between 40 and 200 Hz. Check for rattles, buzzing or voice coil
rub. Reduce the output to 5 watts (6.5 volts). and continue to sweep the range between 200 and 18,000 Hz.

Note: When using a sine wave on the 901 Series III speakersystem. do not operatethe speaker below 40 Hz at levels greaterthan 20 watts (126
volts) as possible damage to the drivers can occur.

. PHASING CHECK - Using a 6 to 20 watt battery or DC Power Supply, check that all speakers are in phase (moving together). Connect the

positive portion of the power supply to the "plus" terminal of the 901 and the ground connection of the supply to the minus terminal of the
speaker system. This will produce an outward motion of all drivers (including the front driver). (See Figure 1).

SERVICE NOTES

Early Production Series I ll drivers are secured by Torxhead screws (Apex Tool No. 440TX15). Authorized serviceagencies have been provided
with this tool. It unavailable, a 3/32 Allen wrench or a 3.7 mm hex metric wrench can be used.

if necessarya #8 Tinnerman clip (013178-8) (Bose P/N 88M) can be used to secure the drivers in the 901 Acoustic Matrix" enclosure. A94 inch
#8 sheet metal screw (Bose P/N 103126-12) is used to secure the drivers when using the Tinnerman clip.

The "c" terminal is provided for future product innovations designed to operate with the 901 Series III. Only use the terminals marked plus" and
minus" for connection to amplifiers or receivers. However, service of the loudspeaker can be facilitated when checking continuity by using the
v." terminal. (See Figure 1 and Test Procedure 1).

The Part I 901 speakers are wired with front speaker (5) connected in series with speakers 6,7,8 and 9. The plus" terminal of the front speaker is
connected to the "w" terminal. (See Figure 1).

The Pan II 901 speakers are wired with front speaker (5) connected in series with speakers 1, 2, 8 and 4. The minus terminal of the front

speaker is connected to the a terminal. (See Figure 1).

901 Ill speakers have been manufactured using both American and metric threaded speaker terminal posts. When replacing terminal knurled
nuts, be certain to use the correct knurled nut. (See Parts List).

STAPLE (e) . . .a-TAPE (10) .

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Figure 3 Front Grille Attachment Figure 4 Rear Grille Attachment

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Bose 901 iii spk service manual

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