Loewe Concertos Acoustimass 61247 Service Manual page 55

3.3 DC Offset
After a successful power-up, confirm that no DC offset exists at each of the six audio out-
puts.
Ground all 6 audio inputs.
Disconnect the loads from the audio outputs.
Apply 5V to all 3 mute inputs to un-mute the amplifiers.
Measure the voltage at each output:
3.3.1 B out, J702_2
3.3.2 L out, J701_2
3.3.3 C out, J701_3
3.3.4 R out, J701_4
3.3.5 LS out, J701_8
3.3.6 RS out, J701_6
3.4 Bass channel gain (unloaded)
Apply +5V to the mute inputs to un-mute the bass amplifier.
Disconnect the 4W load from the output of the bass amplifier.
Apply a 200mVrms sine wave to the bass amplifier input.
Measure the gain (relative to the input signal) at the bass amplifier output at the following
frequencies:
3.4.1 20Hz
3.4.2 300Hz
3.5 Bass channel noise (unweighted RMS)
Apply +5V to the mute inputs to un-mute the bass amplifier.
Disconnect the 4W load from the output of the bass amplifier.
Short the bass channel input to ground.
Measure the unweighted noise at the bass channel output:
3.5.1 bass channel output noise
3.6 L,C,R,LS,RS channel gain (unloaded)
Apply +5V to the mute inputs to un-mute the amplifiers.
Disconnect the 8W load from the output of the L,C,R,LS,RS amplifiers.
Apply a 200mVrms, sine wave to the L,C,R,LS,RS amplifier inputs in turn.
Framingham, MA 01701-9168
|dc offset| < 20mV
|dc offset| < 20mV
|dc offset| < 20mV
|dc offset| < 20mV
|dc offset| < 20mV
|dc offset| < 20mV
gain 21.5dB ± 2dB
gain 21.5dB ± 2dB
< 2mV
SIZE FSCM CLASS
A 32108
DWG NO.
TS 197297
SHEET REV.
55
00
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