Bose Life CD5 Series I Service Manual page 26

5. Headphone Mute
5.1 Select the AUX input.
5.2 Apply a 500mVrms, 1kHz signal to the
L/R AUX input.
5.3 Insert a mini-jack into the headphone
output. The A output should mute.
FM ALIGNMENT TESTS AND
ADJUSTMENTS
Unless otherwise noted, set an RF genera-
tor to 98.1MHz, 40dBf, 1kHz, mono modu-
lation, pilot off, 100% (75kHz deviation).
1. Front End Mixer Coil Adjustment
1.1 Adjust the FM front end (TUNER) mixer
coil until a maximum DC voltage is mea-
sured at U301 pin 25. Adjust the coil until
the voltage comes within +0, -20mV of the
peak voltage.
2. FM Detector Zero Adjust and Distortion
Adjustment
2.1 Set the RF generator to 65dBf.
2.2 Adjust T305 until the voltage reads
0Vdc ± 110mVdc across C317+ (AFC test
point) and C322+ (VREG test point).
2.3 Adjust T304 for minimum distortion. The
distortion should be < 0.4%.
2.4 Repeat this procedure until optimal
results are obtained.
3. FM Stop Level Adjustment
3.1 Set the RF generator to 31dBf.
3.2 Rotate R334 counterclockwise until the
voltage at U301 pin 21 drops below 2.5Vdc.
Then rotate R334 clockwise until the
voltage goes above 2.5Vdc.
Note: The correct adjustment is at the point
just after the voltage switches high.
TEST PROCEDURES
25
3.3 Adjust the generator's output to 35dBf.
Verify that U301 pin 21 is < 2.5Vdc.
4. Stereo Separation
4.1 Set the RF generator to 65 dBf, pilot on,
left modulation, 1kHz, 100% (75kHz devia-
tion).
4.2 Reference a dB meter to left FIXED
output.
4.3 Measure the right FIXED output. It
≤
should be -25dB.
Note: If the unit fails this test, perform the
following procedure.
1. Change R354 to a 560Ω, 5%, 1/10.
2. Remove W302.
3. Add R355 (a 1kΩ, 10%, 1/2 W potenti-
ometer). Adjust R355 for maximum separa-
tion. This option is listed on note 9 of the
schematic.
5. FM Sensitivity
5.1 Set the RF generator to 42dBf, L= -R
modulation, pilot on.
5.2 Reference a dB meter to the left FIXED
output.
5.3 Measure the noise (with modulation off
and pilot on) at the right FIXED output. The
SNR should be > 50dB for the 120V ver-
sion and > 45dB for the 220V version.
Note: If the unit fails this test, the FM front
end should be replaced.