Front Circuit(Digitron & Key) - NAD T571C Service Manual

4. Front Circuit (Digitron & key)
START
Power on.
LED ON?
YES
Is Digitron on normally?
YES
Do all the
buttons work
normally?
YES
Check waveform of
Check and replace
R926, R925.
Does remote control
work normally?
YES
Complete repairing Front B/D.
NO
Is oscillation of
X901 normal?
NO
Check waveform
of IC901 Pin 6.
CD
NO
Is waveform of IC901
Pin 40 normal?
NO
IC901 Pin 21, 22.
YES
Solder defective parts again.
NO Does pulse
waveform of RC901 Pin 1
appear?
YES
Is IC901
Pin 17 connected to
RC901 Pin 1 ?
YES
Replace IC901.
YES
NO
YES
NO
YES
NO
YES
NO
Is RC901 Pin 2 5V?
Replace RC901.
Re-solder.
3-7
Check Power.
Replace IC902.
Check waveform
of IC901 Pin 22.
YES
Solder Key part.
Replace IC901.
Check waveform
of IC901 Pin 27.
YES Replace IC901.
Replace LED901.
NO
Solder defective parts
YES
YES
YES
NO
NO
Recheck