Bose 251 Manual - Página 4

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251 Environmental Speaker 256033

1. Woofer Rub and Tick Test

1.1 Apply a 6 Vrms, 10 Hz signal to the

speaker input terminal. No extraneous noises

such as rubbing, scraping or ticking should be

heard.

Note: To distinguish between normal suspen-

sion noise and rubs or ticks, slightly displace

the cone of the woofer with your fingers. If the

noise can be made to go away or get worse,

it is a rub or tick and the woofer should be

replaced. If the noise stays the same, it is

normal suspension noise and the woofer is

okay. Suspension noise will not be heard with

program material.

2. Air leak Test

2.1 Apply an 8 Vrms, 65 Hz signal to the

speaker input terminal.

2.2 Listen for air leaks around the cabinet

seams, Twiddler™ panel, and the woofer and

Twiddler gaskets. Reposition or replace any

gasket that is found to leak. Repairs made to

the cabinet seam should not be visible from

the exterior of the speaker.

Note: A whooshing noise from the ports at

approximately 65 Hz and 185 Hz is accept-

able (port tuned frequencies).

3. Twiddler Phase Test

3.1 Check the wiring of the Twiddler against

Figures 1 and 2.

4. Sweep Test

4.1 Apply an 8 Vrms, 10 Hz signal to the

speaker input terminal.

4.2 Sweep the signal generator from 10 Hz to

5 kHz and then back to 10 Hz.

4.3 Apply a 3 Vrms, 5 kHz signal to the

speaker input terminal.

4.4 Sweep the signal generator from 5 kHz to

15 kHz and then back to 5 kHz.

TEST PROCEDURES

4.5 Listen for buzzes, rattles or other noises.

Redress any wire that buzzes; replace the

woofer or Twiddler if they are found to be

defective.

5. Woofer Phase Test

5.1 Observing polarity, momentarily apply 8

VDC to the speaker input terminal.

Note: To avoid damaging the speaker, only

momentarily apply the DC voltage.

5.2 The woofer should move outward with the

application of the DC voltage.

PTC

Yellow

Woofer

Green

Black

Figure 2. Schematic Diagram

Red

Gray

Twiddlers

33uF, BP