Bose 300PM Panduan Servis - Halaman 7

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Halaman Cetak

Power Amplifier

Frequency

Generator

Figure 1. Model 300PM Loudspeaker test

setup diagram

Note: Refer to Figure 2. Model 300PM

driver wiring diagram for the following

procedure.

1. Phase Test

1.1 Remove the speaker grille using

Disassembly/Assembly procedure 1.

1.2 Observing polarity, apply a +6Vdc level

to the input terminals on the rear of the

loudspeaker. The drivers should both

move outward.

1.3 Replace the grille using procedure 2.

Note: Refer to Figure 1. Model 300PM

Loudspeaker test setup diagram, for the

following tests.

2. Rub and tick test

2.1 Remove the grille using procedure 1.

2.2 Apply a 6Vrms, 10Hz signal to the

input terminals on the rear of the speaker

cabinet.

2.3 Listen carefully for any buzzes, rattles,

or other extraneous noises from the drivers

or trim parts.

Note: There is a normal suspension noise.

To distinguish between a rub or a tick and

suspension noise, displace the driver cone

slightly with a finger. If the noise stays the

same, it is suspension noise.

TEST PROCEDURES

DMM

Loudspeaker

2.4 Replace the grille using procedure 2.

3. Air Leak Test

3.1 Remove the grille using procedure 1.

3.2 Apply a 6Vrms, 60Hz signal to the

input terminals on the rear of the speaker

cabinet. Leave the speaker port open.

3.3 Test duration should be 5 seconds

minimum.

3.4 Listen carefully for air leaks along all

glue joints, at the binding post connector,

and at both transducer mounting locations.

Air leaks will be heard as a hissing or

sputtering sound. All repairs must be

hidden.

3.5 Replace the grille using procedure 2.

4. Power Sweep Test

4.1 Apply a 6Vrms, 10Hz signal to the

input terminals on the rear of the speaker

cabinet. Leave the speaker port open.

4.2 Sweep the input frequency from 10Hz

to 3kHz.

4.3 Reduce the input voltage level to

4Vrms and sweep the oscillator from 3kHz

to 5kHz.

Note: The whooshing noise from the port

at approximately 60Hz is acceptable.

4.4 Replace any transducer that has a

buzzing noise. There shall not be any

buzzes or rattles from the internal

connecting wires or components.

Redress any buzzing wires.