Amplifier Test Procedures - Bose Loewe Concertos Acoustimass 61247 Service Manual

Note: Unless you are testing the amplifier for its rated power output, all tests are to be performed
with the speaker outputs unloaded. The amplifier can be tested with loads as long as the PCB is
still mounted in its heatsink.
Output
Bass Channel output
Left Channel output
Right Channel output
Center Channel output
Left Surround output
Right Surround output
1. Bass Channel Gain Test
1.1 Apply a 200 mVrms, 300 Hz signal to
the input wires for the bass channel input
at connector J700 pins 8 (signal) and 11
(ground). Also ground pin 11 to the
shield.
1.2 Reference a dB meter to the input.
Measure the gain at the output.
It should be +21.5 dB ± 2 dB.
1.3 Change the input signal to 20 Hz.
Reference a dB meter to the input.
Measure the gain at the output.
It should be +21.5 dB ± 2 dB.
2. Left, Right, Center and Surround
Channel Gain Test
2.1 Apply a 200 mVrms, 100 Hz signal
to the input wires on connector J700
pins 6 (RS), 7 (LS), 9 (C), 10 (L), 12 (R)
and pin 11 (ground).
2.2 Reference a dB meter to the input.
Measure the gain at the output of each
channel. It should be +11.5 dB ± 2 dB.
2.3 Change the input signal to 15 kHz.
Reference a dB meter to the input.
Measure the output of each channel. It
should be +11.5 dB ± 2 dB.
3. Bass Channel Distortion Test
3.1 Connect a 4 Ohm load to the Bass
channel output at J703 pins 1 (-) and 2 (+).

Amplifier Test Procedures

Speaker Load Table
Location
J703 pin 2 + , J703 pin 1 -
J701 pin 2 + , J701 pin 5 -
J701 pin 4 + , J701 pin 5 -
J701 pin 3 + , J701 pin 1 -
J701 pin 8 + , J701 pin 7 -
J701 pin 6 + , J701 pin 7 -
12
Recommended Load
4 Ohm, 1%, 100 Watts
8 Ohm, 1%, 50 Watts
8 Ohm, 1%, 50 Watts
8 Ohm, 1%, 50 Watts
8 Ohm, 1%, 50 Watts
8 Ohm, 1%, 50 Watts
3.2 Apply a 100 mVrms, 100 Hz signal to
the input wires for the bass channel input
at connector J700 pins 8 (+) and 11 (-).
3.3 Measure the distortion at bass chan-
nel output. It should be <0.4% at 0.5
Watts output.
3.4 Change the input level to 1.35 Vrms.
3.5 Measure the distortion at the bass
channel output. It should be <0.3% at
65 Watts output.
4. Left, Right, Center and Surround
Channel Distortion Test
4.1 Connect each of the outputs to an
8 Ohm load. Apply a 533 mVrms, 1 kHz
signal to the input wires at connector
J700 pins 6, 7, 9, 10, 12 and 11.
4.2 Measure the distortion at the outputs.
It should be < 0.3% at 0.5 Watts output.
4.3 Change the input level to 4.1 Vrms.
4.4 Measure the distortion at the outputs.
It should be < 0.3% at 30 Watts output.
5. DC Offset Test
5.1 Disconnect all loads. Ground all audio
inputs and apply a 5 Volt DC signal to the
mute lines pins 2, 3 and 4.
5.2 Measure the DC offset on all the
outputs, it should be < 20 mVdc.