Sharp BD-HP22SB Service Manual page 20

BD-HP22SB
5. POWER UNIT
FLOW CHART No.1
Is the fuse working properly?
Does the power come back if the power cable is unplugged
and plugged again after several seconds?
Is AT_5V line working normally?
Is voltage normal at lines AT_14V, BD_12V, AT_9V, BD_5V,
SUB_PC_5V, AT_-12V and SUB_PC_-8V?
Is pin (19) of IC2504 at "H" level?
FLOW CHART No.2
Is a part of primary circuit causing leaks, short-circuit or open
circuit (L901, L902, D901, T901, IC901, C911 and their
peripheries)?
FLOW CHART No.3
Is AT_5V line working normally?
When the Power key (S1201) is pressed, is pin (75) of IC2504
at "L" level?
Is pin (59) of IC2504 at "H" level?
Is ST_5V output?
Is pin (76) of IC2504 at "H" level?
Is the DRIVE_P-CON(H) line at "H" level?
Are BD_12V and BD_5V output?
Check or replace the peripheral circuits of IC2504.
FLOW CHART No.4
Check if the rectifier diode and the circuit are causing short-circuit, or if the shunt regulator circuit is defective, in each rectifier circuit of the
secondary circuit (around D952, 953, 954, 955 and 951).
Power does not come ON.
YES
YES
YES
YES
The fuse blows.
Case(1)
The power does not come ON from power OFF status.
YES
YES
YES
YES
YES
YES
YES
Buzzing sound is generated near the power circuit.
NO
If the fuse still blows after replacement, refer to "The fuse blows" in
the FLOW CHART No.2.
NO
Is a part of primary circuit causing leaks, short-circuit or open circuit
(L901, L902, D901, T901, IC901, C911 and their peripheries)?
NO
Check D954, L953, C960 and C963 of the AT_5V line.
NO
Check each rectifier circuit and SW circuit of the secondary circuit.
NO
Check the power failure detection circuit (IC2508 and its periphery).
Check if the rectifier diode and the circuit are causing short-circuit in
each rectifier circuit of the secondary circuit. (D952, D953, D954,
D955)
NO
Check the rectifier circuit of AT_5V and if there is a short-circuit in
the secondary circuit side.
NO
Check the line between S1201 and IC2504.
NO
Check the function of Microcomputer in IC2504 and its peripheral
circuits.
NO
Check the SUB_PC_5V circuits (Q9501 and its periphery).
NO
Check the peripheral circuits of IC2504.
NO
Check Q912 and the peripheral circuits.
NO
Check the BD_12V and BD_5V circuits (Q904, Q913, etc.).
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Case(2)