28
BDP-120
1
2
3
4
A
B
C
D
E
F
1
2
3
4
[4] POWER PWB Unit
A button fails to work.
Is the button switch contact and tightness as specified?
YES
YES
Check the line between each button and IC2503. Or check the
pull-up resistor at pin (72) of IC2503. (R257
8
)
Is the control voltage properly applied at pin (72) (KEY_EJCT)
and pin (73) (KEY_STBY) of IC2503? (While the relevant
button is held down, the "H" level changes to "L" level.)
N
O
Check the relevant switch. Replace it as required.
N
O
Check IC2503 and its peripheral circuits. Or replace IC2503
as required.
FLOW CHART No.6
Power does not come ON.
Is the fuse working properly?
If the fuse still blows after replacement, refer to "The fuse blows" in
the FLOW CHART
N
o.2.
Does the power come back if the power cable is unplugged
and plugged again after several seconds?
Is a part of primary circuit causing leaks, short-circuit or open circuit
(L901, L902, D901, T901, IC901, C911 and their peripheries)?
Check D952, L951, C955, C95
8
and C961 of the AT_12
V
line.
YES
N
O
Check the power failure detection circuit (IC250
8
and its periphery).
N
O
N
O
N
O
Is AT_12
V
line working normally?
Is voltage normal at lines AT_-12
V
and SUB_PC_-
8V
?
Check each rectifier circuit and SW circuit of the secondary circuit.
YES
YES
YES
Is pin (17) of IC2503 at "H" level?
YES
Check or replace the peripheral circuits of IC2503.
N
O
FLOW CHART No.1
The fuse blows.
Is a part of primary circuit causing leaks, short-circuit or open
circuit (L902, L901, D901, T901, IC901, C911 and their
peripheries)?
Check if the rectifier diode and the circuit are causing short-circuit in
each rectifier circuit of the secondary circuit. (D952)
Case(2)
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