Bose 3-2-1GS Series II Service Manual page 57

8.4 Change the RF frequency to 600 kHz
(US, Dual) or 603 kHz (Euro, UK, AUS and
Japan) and re-tune the console to 600 kHz
or 603 kHz (as appropriate).
8.5 Adjust the black slug (T2000) for maxi-
mum level. Verify that the level is greater
than 40 mVrms.
8.6 Repeat steps 8.2 to 8.5 until maximum
audio output is obtained without the need for
further adjustment.
8.7 Replace the metal top cover over the RF
circuitry. Re-install the tuner PCB into
the console before continuing testing.
9. AM Sensitivity
9.1 Inject a 1080 kHz RF signal at a level
of 55 dBuV emf, 30% modulation, 1 kHz
modulation frequency.
9.2 Tune the console to 1080 kHz.
9.3 Measure the output level at the the
console test cable audio output jacks. It
should be between 70 and 320 mVrms.
9.4 Measure the distortion level of the output
at the console test cable analog audio output
jacks. It should be 10.0% max.
FM Adjustments
Note: Unless otherwise noted, set the RF
generator for 1 kHz, mono modulation, pilot
off and 75 kHz deviation. Power levels for
FM testing are given in dBf at the antenna
input to the unit.
Typically a test setup will consist of an RF
generator with a 50 Ohm output impedance
and a 50 Ohm to 75 Ohm impedance match-
ing element. The two most commonly used
impedance matching element are a resistive
network which has a 5.7 dB insertion loss or
a "lossless" transformer which has a
0.5 dB insertion loss.
TEST PROCEDURES
57
To find the required setting in dBuV emf from
a given dBf value for an RF generator with a
50 Ohm output impedance use the conver-
sions in the following table.
Using a Subtract 1.3 dB. eg:
"lossless" 65dBf => set generator
transformer to 66.8 dBuV emf
Using a resistive Subtract 6.5 dB eg:
network 65dBf => set generator
(5.7dB loss) to 71.5 dBuV emf
Note: For generators with RF level resolu-
tions of only 1 dB, round up.
10. FM Distortion Measurement /
Adjustment
10.1 Inject a 98.1 MHz, 1 kHz mono, 75 kHz
deviation, pilot off (83.0 MHz Japan units),
RF signal at a level of 58 dBuV emf into
J2001.
10.2 Tune the console to 98.1 MHz
(83.0 MHz Japan units).
10.3 Measure the distortion plus noise
(THD+N) at the audio output jacks. If it is
less than or equal to 0.60%, verify that
the audio level is between 520 and 1050
mVrms. If these are not the measurements
you have, proceed to step 12.4.
10.4 If the THD+N is greater than 0.65%, or
the audio level is less than 520 mV, adjust
T2002 for minimum distortion. Verify that
the level is greater than 520 mV and the
distortion is less than 0.65%.
12. FM Sensitivity
12.1 Inject a 98.1 MHz (83 MHz for Japan
units) RF signal at a level of 13 dBuV emf
into J2001.
12.2 Measure the THD+N at the console
test cable audio output jacks. It should be
less than or equal to 3.0%.