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FLOW CHART NO.1
No power
NO
Is the fuse good?
YES
Is the normal state restored when
NO
once unplugged power cord is
plugged again after several
seconds?
YES
NO
Are AT 5V voltage line normal?
YES
Are AT 44V, AT 23V, AT 12V,
NO
AT –24V and filament voltage lines
normal?
YES
Is "H" level applied at pin(1) of
NO
IC701?
FLOW CHART NO.2
Fuse blown out.
Case (1)
Check for leak or short-circuiting of
primary circuit part.
(L901, D901~904, T901, C906,
R904, Q901~902 and etc.)
FLOW CHART NO.3
When the output voltage fluctuates.
Check whether the secondary side
NO
photocoupler circuit operates
normally.
YES
Check whether the primary side
NO
photocoupler output control
functions normally.
YES
Replace IC901.
The fuse blows out even when it is
replaced with new one.
See FLOW CHART NO.2
<Fuse blown out.>.
Check for leak or short-circuiting
of primary circuit part.
(L901, D901~904, T901, C906,
R904, Q901~902 and etc.)
Check each rectifier circuits and
short-circuit of secondary circuit.
Check the power failure circuit.
(Q705)
Case (2)
Check for short-circuiting of
rectifying diode and circuit in each
rectifying circuit of secondary circuit.
(D921~928)
Check the circuit and replace parts.
(IC901, IC903, etc.)
Check the circuit and replace parts.
(IC901, IC903, Q902, T901 and etc.)
FLOW CHART NO.4
When buzz is heard from the vicinity of power circuit.
Check for short-circuiting of circuit and rectifying diode of each rectifying circuit of secondary
circuit and check for failure of shunt regulator circuit. (D921~928, IC903, C932 and C933)
FLOW CHART NO.5
The fluorescent display tube fails light up.
Is the supply voltage of 5V feed to
NO
pin(8) of IC801?
YES
Is the supply voltage of –24V
NO
feed to pin(1) of IC801?
YES
Is it possible to confirm signals
NO
FIP CS, FIP OE, FIP DATA, and
FIP CLK on the pins(2), (3), (5) and
(6) of IC801?
YES
Are grid and segment signals
NO
supplied to the indication tube
(DG801) from the indication
tube driver IC (IC801)?
YES
Is supply filament voltage feed
NO
between pin(1)/(2) and (31)/(32)
of the flourescent display tube?
YES
Check the periphery of fluorescent
indication tube and main block.
NO
Check that the fluorescent indication
tube is free from damages such as
crack.
Check AT 5V line.
Check AT –24V line.
Check signal line between IC701
and IC801.
Replace IC801.
Check power circuit and D952.
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