39
VC-A422U
VC-H822U
7.
TR
OUBLESHOO
TING
FLOW CHART NO.1
No power
The fuse blows out even when it is
replaced with new one.
See
FLOW CHART NO.2
<Fuse blown out.>.
YES
YES
YES
YES
NO
NO
NO
NO
NO
Is the fuse good?
Is the normal state restored when
once unplugged power cord is
plugged again after several
seconds?
Check for leak or short-circuiting
of primary circuit part.
(L901, D901~904, T901, C906,
R904, Q901~902, etc.)
Are AT 5V voltage line normal?
Are AT 44V, AT 27V, PC 12V,
normal?
Check each rectifier circuits and
short-circuit of secondary circuit.
Is "H" level applied at pin(95) of
IC701?
Check the power failure circuit.
(Q705)
FLOW CHART NO.3
When the output voltage fluctuates.
Check whether the secondary side
photocoupler circuit operates
normally.
Check the circuit and replace parts.
(IC901, IC903, etc.)
NO
YES
Check whether the primary side
photocoupler output control
functions normally.
Check the circuit and replace parts.
(IC901, IC903, Q902, T901, etc.)
NO
YES
Replace IC901.
FLOW CHART NO.2
Fuse blown out.
Case (1)
Case (2)
Check for leak or short-circuiting of
primary circuit part.
(L901, D901~904, T901, C906,
R904, Q901~902, etc.)
Check for short-circuiting of
rectifying diode and circuit in each
rectifying circuit of secondary circuit.
(D921~924)
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. (D921~924, IC903, C932, C933)
NO
NO
NO
NO
The LCD display foils light up
Is the supply voltage of 5V feed to
pin (32) IC8001?
Check STBY 5V line
Is the supply voltage of 3.4V, 1.7V
feed to pin (38) and pin (39) of
2C8001.
Check pins(38), (39) of 2C8001
and perifheral circuits.
Is it possible to confirm signals LCD
RESET, LCD CS, LCD CLOCK and
LCD DATA on the pins(36), (42),
(43) and (44) of IC8001?
Check the signal line between
IC701 and 2C8001.
NO
Check peripheral circuit of pin(41)
of IC8001.
Replace IC8001
Is the OSC signal at pin(41) of
IC8001 present?
Are the segment signals supplied
to the LCD display (LC8001) from
the driver 2C(IC8001)?
Check that the LCD display is free
from damages such as crack
YES
YES
YES
YES
YES
Summary of Contents for VC-A422U
Page 51: ...VC A422U VC H822U VC A422U VC H822U 52 53 SIGNAL FLOW BLOCK DIAGRAM VC A422U ...
Page 52: ...VC A422U VC H822U VC A422U VC H822U 54 55 SIGNAL FLOW BLOCK DIAGRAM VC H822U ...
Page 53: ...56 VC A422U VC H822U POWER CIRCUIT BLOCK DIAGRAM ...
Page 63: ...72 VC A422U VC H822U M E M O ...
Page 76: ...85 VC A422U VC H822U M E M O ...
