Bose Lifestyle CD5 Series I, Service Manual

Page: 27 / 70

26
AM ALIGNMENT PROCEDURES
Test setup: Connect the generator to a
standard radiating loop. Unless otherwise
noted, set an RF generator to 70dBu field
strength, 400Hz, 30% modulation.
See Figure 9.
Figure 9. AM Test Setup
The equivalent field intensity is 26dB less
than the generator output level or 1/20
th of
the output voltage.
1. AM Sensitivity Alignment
1.1 Set the RF generator so that the field
strength at the unit's antenna is 70dB
µ
(70dB
µ
V/M).
STANDARD
SIGNAL
GENERATOR
STANDARD
SIGNAL
GENERATOR
60cm
TEST
LOOP
(PLAN VIEW)
(SIDE VIEW)
Figure 10. Audio PCB Test Section
TEST PROCEDURES
1.2 Reference a dB meter to the Fixed level
output.
1.3 Shut off the modulation and measure
the noise. The SNR should be > 30dB.
2. AM Stop Level Adjustment
2.1 Set the RF generator so that the field
strength at the unit's antenna is 59dB
µ
(59dB
µ
V/M).
2.2 Rotate R339 counterclockwise until the
voltage measured at U301 pin 21 goes
below 2.5Vdc. Then, rotate R339 clockwise
until the voltage goes above 2.5Vdc.
Note: The correct adjustment is at the point
just after the voltage switches high.
2.3 Adjust the field strength to 64 dB
µ
(64 dB
µ
V/M). Verify that the voltage at
U301 pin 21 is < 2.5Vdc.