Troubleshooting Guide - NAD C 725BEE Service Manual

PUSH THE POWER SWITCH TO ON
NO
IS THE 3-COLOUR-LED AMBER LIGHT?
CAN PRESSING ANY KEY TO MAKE
THE UNIT WORK NORMALLY?
NO
IS THE SPK OUT NORMAL?
YES
IS THE SPK OUT NORMAL WHEN
NO
INPUT IS TUNER
YES
NO
IS THE REMOTE CONTROL OK?
YES
NO
IS THE +12V SUPPLY NORMAL?
YES
OK

TROUBLESHOOTING GUIDE

IS IT RED?
YES
ARE ALL POWER SUPPLIES OK?
YES
IS THE 3-COLOUR-LED RED AFTER
SHORT WORKING
YES
IS THERE ''PROTECT!'' FLASH ON VFD?
NO
IS THE OUTPUT DC LEVEL NORMAL?
YES
IS THERE SIGNAL OUTPUT?
YES
IS THE THD BAD?
NO
IS THE IDLE CURRENT NORMAL?
YES
IS THE CABLE FROM TUNER MODULE
TO KEYBOARD OK?
YES
IS THE IR IN/OUT NORMAL?
YES
IS THE REMOTE HANDSET ITSELF
NORMAL?
YES
NO
IS IT BLUE
YES
NO
NO
YES
NO
IS THE DC SERVO CIRCUIT OK?
YES
NO
IS THE POWERAMP INPUT NORMAL?
YES
IS THE MUTE SIGNAL HIGH LEVEL?
YES
IS THE VOLUME CONTROL CIRCUIT
NORMAL?
YES
IS THE TONE DEFEAT CIRCUIT
NORMAL?
YES
IS THE PREAMP MODULE NORMAL?
YES
YES
IS THE S/N BAD?
NO
NO
NO
NO
NO
NO CHECK THE +5V SUPPLY
(POWER BOARD)
CHECK THE LED CONTROL CIRCUIT
AND PROTECTION CIRCUIT
CHECK ALL POWER SUPPLIES
CHECK KEY CIRCUIT
CHECK THE PROTECTION CIRCUIT
CHECK THE MAIN TRANSFORMER
AND POWER BOARD
NO
CHECK THE DC SERVO CIRCUIT
CHECK THE AMP CIRCUIT SECTION
NO
CHECK THE PREAMP CIRCUIT SECTION
NO
CHECK THE MUTE CIRCUIT
NO
CHECK THE VOLUME CONTROL CIRCUIT
NO
CHECK THE TONE DEFEAT CIRCUIT
NO
CHECK THE PREAMP MODULE
CHECK THE AMP CIRCUIT SECTION
YES
TURN THE TRANSFORMER
CHECK THE AMP CIRCUIT SECTION
ADJUST THE IDLE CURRENT OR
CHECK THE IDLE CURRENT CIRCUIT
CHECK OTHER PATRS OF THE
AMP SECTION
CHECK THE CABLE
CHECK THE TUNER MODULE
CHECK THE IR IN/OUT CIRCUIT
CHECK THE HANDSET ITSELF
CHECK THE KEY BOARD AND MCU
CHECK THE +12V SUPPLY CIRCUIT
(POWER BOARD)