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Troubleshooting - Yamaha MX-D1 Service Manual

Digital power amplifier
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Table of Contents
I TROUBLESHOOTING
No Power or Power
shuts off immediately
With the power turned
off, discharge C196 –
C199, C222 and C223
Short circuit between
Drain and Source in FET
(Q117 – Q120)?
NO
Output power supply
is normal?
NO
Remove CB106
Check between R221 and
TP304 with the oscilloscope
Check between R222 and
TP304 with the oscilloscope
Is the Power
oscillation 88 kHz?
(Pulse wave 0 - 15 V)
NO
Q126, Q127 is
short circuit?
NO
Failure in either
IC127, IC128, IC129,
Q128, Q129, Q130, Q131
Refer to "SERVICE
PRECAUTIONS"
on page 8.
YES
Replace the
shorted FET
YES
Note: Connect TP304 to the grounding side of the oscilloscope.
The grounding side of the oscilloscope must be floated
because TP304 is not ground level.
YES
Problem in secondary
power supply
YES
Replace defective
Q126, Q127
Are R560 and
R561 open?
NO
Power on but no
sound from SP
With the power turned
Refer to "SERVICE
off, discharge C196 –
PRECAUTIONS"
C199, C222 and C223
on page 8.
YES
Output coil (L101)
350 kHz pulse available?
NO
YES
FET (Q117 – Q120)
are open?
NO
Failure in IC118,
IC119 or IC107
YES
Replace
R560 and R561
MX-D1
Failure in Analog
amplifier around
input section
Replace the
open FET
15

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