Loewe 67501 D 00, Service Manual

Page: 16 / 61

67501 T/D 00
2 – 7
[3] POWER
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 No.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 D954, L953, C960 and C963 of the AT_5V line.
YES
NO
Check the power failure detection circuit (IC2508 and its periphery).
NO
NO
NO
Is AT_5V line working normally?
Is voltage normal at lines AT_14V, BD_12V, AT_10V, BD_5V,
SUB_PC_5V, AT_-12V and SUB_PC_-8V?
Check each rectifier circuit and SW circuit of the secondary circuit.
YES
YES
YES
Is pin (19) of IC2504 at "H" level?
NO
FLOW CHART No.1
The fuse blows.
Is a part of primary circuit causing leaks, short-circuit or open
circuit (L901, L902, 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, D953, D954,
D955)
Case(1) Case(2)
FLOW CHART No.2
The power does not come ON from power OFF status.
Is AT_5V line working normally? Check the rectifier circuit of AT_5V and if there is a short-circuit in
the secondary circuit side.
Check the function of Microcomputer in IC2504 and its peripheral
circuits.
When the Power key (S1201) is pressed, is pin (75) of IC2504
at "L" level?
YES
NO
NO
NO
Is pin (59) of IC2504 at "H" level?
Is ST_5V output?
Check the line between S1201 and IC2504.
NO
Check the SW circuits (Q2507, 2508) of ST_5V.
YES
YES
Is pin (76) of IC2504 at "H" level?
NO
Check the peripheral circuits of IC2504.
YES
Is the DRIVE_P-CON(H) line at "H" level?
NO
Check the peripheral circuits of IC2503.
YES
Are BD_12V and BD_5V output?
NO
Check the BD_12V and BD_5V circuits (Q904, Q913, etc.).
YES
Check or replace the peripheral circuits of IC2504.
YES
FLOW CHART No.3