60
SC-LX81
1
2
3
4
A
B
C
D
E
F
1
2
3
4
Amplifier Diagnosis with Current Applied (2)
N
o
Yes
Is the modulator IC
power ±5
V
supplied?
(Pins 1 and 3 of C
N
4902)
W
hen the remained switching waveform is not observed in the speaker output, the amplifier is not operating.
Here, confirm that the power and signal necessary for the amplifier to operate are supplied.
Check the path (cables and connectors) of ±5
V
.
N
o
Yes
Is there disable
control signal? (Are pins 1 - 4
of C
N
4000 set to H?)
Check the path (cables and connectors) of the disable signal.
Perform
Amplifier Diagnosis
without Current Applied
N
o
Yes
Is the
driver power supplied?
(About 10
V
between the pins 1
and 2 of C
N
4901.
N
ote that
it is not based on the
chassis)
Diagnose the driver power circuit. (It is highly suspected that there is a failure in
the power amplifier upon the power failure. Also, diagnose the amplifier circuit by
Amplifier Diagnosis without Current Applied
.)
N
o
Yes
Does the
output stage power
±64
V
supplied?
(Pins 1 and 4 of
C
N
4900)
Diagnose the power circuit in the output stage. (It is highly suspected that there is
a failure in the power amplifier upon the power failure. Also, diagnose the amplifier
circuit by
Amplifier Diagnosis without Current Applied
.)