Electrical Troubleshooting Guide; Power Check Flow - NAD M5 C/AH Service Manual

ELECTRICAL TROUBLESHOOTING GUIDE

1.Power check flow

Digital circuit supply
A.
No VF+
Is 5VD section working?
YES
Check D910
No
Replace D910
Analog circuit supply
A.
No +/-12V
Is +/-VCCA works well?
YES
Check U605 U606
Replace U605/U606
NO
No 5VD
Check FH900
Is there a AC voltage at
one terminal of RT900?
YES
Is there a DC voltage At
(+) terminal of B900?
YES
Replace U900.
NO
Is 5VD right
Check Q619 Q621 Q623
Check Transformer
3-2
B.
NO
NO
NO
NO
B.
NO
Yes
NO
Yes
No 5VS
Is 5VD section working?
YES
Is 5VD present at input
of U911?
YES
Replace U911.
YES
Replace RT900.
YES
Replace B900.
No 5VA
Is VM works well
YES
Check U658
YES
Replace U658.