Bose Acoustimass 3 Series Service Manual - Page 21
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3. Tone Control Test
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 100
Hz,220 mVrms.
B. Rotate the bass control knob fully clockwise
and counterclockwise from its center or "normal"
position. The bass level should increase and
decrease cleanly without making a scratchy
noise. Clean or replace any potentiometer that
makes this noise.
C. Repeat this procedure for the treble control
using a frequency of 4 kHz.
4. 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,200 mVrms. Connect a piece of test
equipment capable of measuring decibels to
either the left or right twiddler output terminals
(labeled "To Cube Speakers"). Measure the dBs
at this setting and use as a 0 dB reference.
B. Once connected to either the left or right "cube
speaker" output terminals,adjust the oscillator
frequency and measure the relative response
according to the chart located at the end of this
procedure.
C. Repeat this test for the other channel.
Frequency
100 Hz
200 Hz
360 Hz
Relative Response
-16.0 dB ± 2.0 dB
+5.7 dB ± 1.5 dB
-2.0 dB ± 1.5 dB
20
Frequency
1 kHz
2 kHz
10 kHz
20 kHz
5. Twiddler Power Output Test
NOTE: This test can be performed with a fully
assembled module.
Ω
A. Connect a 4
resistive load across either the
left or right twiddler output terminals (labeled "To
Cube Speakers"). Connect a voltmeter across
the load.
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, 549 mVrms.
C. Measure the voltage across the load. It should
be approximately 8.9 volts (20 watts).The signal
should look undistorted when viewed on an
oscilloscope.
6. Twiddler Short Circuit Protection Test
NOTES: This test can be performed with a fully
assembled module.
Do not short out for longer than 1 second.
A. Adjust the oscillator to 1 kHz, 200 mVrms.
Short the left or right twiddler output terminals.
The signal should mute for approximately 3
seconds.
Relative Response
0 dB
-5.2 dB ± 1.5 dB
+1.0 dB ± 1.5 dB
-1.4 dB ± 2.0 dB