Bose FREESPACE BUSINESS Service Manual - Page 21

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3. Frequency Response of L/R (Twiddler) Channels

NOTE: This test can be performed with a fully

assembled module.

A. Connect an oscillator to the module's L/R

audio input terminals. Adjust the oscillator to 1

kHz,30 mVrms for a 0 dB reference.

NOTE: There are 2 sets of twiddler output

terminals for each channel. Refer to the I/O PCB

Schematic before attempting any connections.

For the left channel,connections should be made

to pins 8 (+) and 5 (-). For the right

channel,connections should be made to pins 4

(+) and 1 (-). This note applies to Procedures 3

through 6.

Ω

B.Connect an 8

resistive load across either the

left or right twiddler output terminals. Using a dB

meter,measure the response according to the

chart given below.

C. Repeat this test for the other channel.

Frequency

100 Hz

210 Hz

320 Hz

1 kHz

1.8 kHz

10 kHz

36 kHz

Relative Response

-17.6 dB ± 2.0 dB

+1.3 dB ± 1.5 dB

- 6.2 dB ± 1.8 dB

0 dB

-6.5 dB ± 1.5 dB

-2.0 dB ± 1.5 dB

-5.3 dB ± 2.0 dB

4. Twiddler Power Output Test

NOTE: This test can be performed with a fully

assembled module. Refer to the second note in

Procedure 3 before making any connections.

Ω

A. Connect an 8

resistive load and a voltmeter

across either the left or right twiddler output

terminals.

NOTE: These measurements can be obtained at

120 and 240 V. Results will vary depending on

the line voltage used.

B. Connect an oscillator to the module's L/R

audio input terminals. Adjust the oscillator to 1

kHz, 465 mVrms.

C. Measure the voltage across the load. It should

be approximately 20 volts (50 watts).The signal

should look undistorted when viewed on an

oscilloscope.

5. Twiddler Short Circuit Protection Test

NOTES: This test can be performed with a fully

assembled module. Refer to the second note in

Procedure 3 before making any connections.

A. Adjust the oscillator to 400 Hz, 180 mVrms.

Ω

Connect an 8

resistive load and a voltmeter

across either the left or right twiddler output

terminals. The output voltage should measure

approximately 8 Vrms. Momentarily short the left

or right twiddler output terminals. The signal

should mute for approximately 2-3 seconds.

6. Compressor Test

NOTE: This test can be performed with a fully

assembled module. Refer to the second note in

Procedure 3 before making any connections.

A. Connect an oscillator to the module's L/R

audio input terminals. Adjust the oscillator to 1

kHz,1.1 Vrms.

Ω

B. Connect an 8

resistive load across either the

left or right twiddler output terminals.