Bose 2150 - Page 51

51
2. Signal Processor PCB Gain Test
2.1 Remove the amplifier top cover using
disassembly/assembly procedure 1.
CAUTION: Components with dangerous
voltages are exposed when operating the
amplifier with the top cover removed.
2.2 On the front panel of the amplifier, set the
gain controls fully CW. On the rear panel, set
the configuration dip switches (7) OFF
(down).
Note: The test points listed below are lo-
cated on the signal processor PCB. This
board is located on the top of the amplifier
RF shield next to the heatsink. Refer to the
circuit board layout diagrams for component
location.
2.3 Apply a 100 mVrms, 1 kHz sine wave test
signal to the left and right amplifier inputs.
2.4 Using an oscilloscope, check for a
100 mVrms
+ 1.3 mV signal at R503 (R502).
Note: The test points listed are in CH1
(CH2) format.
2.5 Set the configuration dip switches on the
amplifier rear panel to OUT FX.
2.6 Using an oscilloscope, check for a
100 mVrms + 1.9 mV signal at U503 pin 5
(U504 pin 5).
2.7 Using an oscilloscope, check for a
365 mVrms + 13 mV signal at U512 pin 1
(U512 pin 7).
2.8 Using an oscilloscope, check for a
581 mVrms + 25 mV signal at U506 pin 5
(U507 pin 5) and U508 pin 5 (U509 pin 5),
regardless of high pass filter selection.
2.9 Replace the amplifier top cover.
TEST PROCEDURES
3. Frequency Response Test
3.1 On the front panel of the amplifier, set
the gain controls fully CW. On the rear panel,
set the configuration dip switches (7) OFF
(down).
3.2 Connect a 4 Ohm load resistor to the left
and right channel 4 Ohm speaker outputs.
3.3 Apply a 400 mVrms, 1 kHz signal to the
left channel input.
3.4 Reference a dB meter to the left channel
output level. This is the 0 dB reference level.
3.5 Slowly sweep the input frequency from
30 Hz to 20 kHz while noting the dB meter
reading. The frequency response should be
0 dB + 0.5, -3.0 dB from 30 Hz to 20 kHz.
3.6 Connect the 4 Ohm load resistor to the
left channel 25V line output. Repeat steps
3.3 to 3.5.
3.7 Repeat steps 3.2 to 3.6 for the right
channel.
4. Harmonic Distortion Test
4.1 On the front panel of the amplifier, set
the gain controls fully CW. On the rear panel,
set the configuration dip switches (7) OFF
(down).
4.2 Connect a 4 Ohm load resistor to the left
and right channel 4 Ohm speaker outputs.
Connect a distortion analyzer in parallel with
the left channel 4 Ohm load resistor.
4.3 Apply a 775 mVrms, 1 kHz signal to the
left channel input.
4.4 Measure the distortion level at the left
channel output. Harmonic distortion should
be < 0.5% (20 Hz to 20 kHz bandwidth).
4.5 Connect the distortion analyzer and 4
Ohm load resistor to the left channel 25V
line output.