Troubleshooting - Marantz MM7055/N1B Service Manual

TROUBLE SHOOTING
1. POWER
1.1. Power not turn on
Power not turn on.
When the AC line turned on, does the
ON/STANDBY indicator on the front
panel light?
YES
Is the PROTECT LED blinked from
power on 7seconds after?
YES
Refer to SPECIAL MODE
-3.SYSTEM ERROR
1.2. Fuse is blown
Check for leaks or short circuits in the
primary side parts, and replace any
defective parts.
NO
Is a DC 5V voltage supplied from the
STANDBY PCB to the μ-com?
YES
Is the "P_DOWN" line Hi(5V)-level?
YES
Does the crystal(X400) oscillate?
YES
Confi rm u-com(IC402) circuit.
NO
Is the primary fuse(F701) blown?
YES
Refer to 1.2.Fuse is blown.
Fuse is blown
Check for short circuits in the rectifi er
NO
diodes and circuitry of the secondary
side rectifying circuits, and replace
any defective parts.
After repairing, also replace the fuse.
23
NO
Confi rm +5V regulator(IC75) circuit.
NO
Confi rm RESET IC(IC71) circuit.
NO
Confi rm crystal (X400) circuit.
Confi rm the connector
NO
from Main Transformer.
(CN11,CN14,CN704,CN72)
Check for short circuits in the power
NO
stabilizer unit's regulator output
terminal and the ground, and replace
any defective parts.