Front Circuit(Digitron & Key) - NAD T572C 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
IC901 Pin 14, 15.
Check and replace
R926, R925.
Does remote control
work normally?
YES
Complete repairing Front B/D.
NO
Is oscillation of
X901 normal?
YES
NO
Check waveform
of IC901 Pin 7.
CD YES
NO
Is waveform of IC901
Pin 20 normal?
YES
NO
YES
Solder defective parts again.
NO Does pulse
waveform of RC901 Pin 1
appear?
YES
Is IC901
Pin 28 connected to
RC901 Pin 1 ?
YES
Replace IC901.
YES
NO
Check Power.
NO
Replace IC902.
NO
Check waveform
of IC901 Pin 15.
Replace IC901.
Check waveform
of IC901 Pin 18, 19.
Replace LED901.
NO
Is RC901 Pin 2 5V?
YES
Replace RC901.
YES
Re-solder.
YES
3-7
NO
YES
Solder Key part.
NO
YES Replace IC901.
NO
Solder defective parts
Recheck