32
DJM-850-K
1
2
3
4
A
B
C
D
E
F
1
2
3
4
5.4 VOLTAGE MONITORING CIRCUIT
This unit monitors the voltages of the main power-supply ICs, using the
V
DET signal.
The
V
DET signal level is high (+3.3
V
) during normal operations.
W
hen the level becomes low (0
V
), detect abnormality
in the MAI
N
UCOM (IC2
8
03).
If power failure is detected with the
V
DET signal, the MAI
N
UCOM will stop supplying the primary source of
power to the main transformer, setting the RELAY_CO
N
T signal to low and interrupting the relay RY3001.
If any voltage is abnormal, that error will be detected by the voltage-monitoring program after it is started after a usual
startup of the unit. Then the power supply to the main transformer will be stopped. For this reason, power will be supplied
for about 1 sec after startup.
Identify which power-supply IC is defective, by turning the unit OFF then back O
N
while monitoring each voltage with an
oscilloscope. Check the value of each voltage immediately before stopping power supply.
Note:
Each time before turning the unit O
N
, make sure that each power-supply IC is not short-circuited to G
N
D.
The MAI
N
UCOM also informs of power failure with flashing of the SETUP button, by sending the STBY_LED signal:
Flashing intervals: 250 ms (lit for 125 ms/unlit for 125 ms)
As the switching-system output is stopped, the indications other than the SETUP LED are unlit and all the switches
and
V
Rs are disabled.
MAI
N
ASSY
V
oltage
monitoring
circuit
H:
N
ormal
L: Abnormal
H: Main trans. is output.
L: Main trans. output is stopped.
P
N
LA ASSY
MAI
N
UCOM
(IC2
8
03)
SETUP LED
D6624 (RED)
IC1404
PRIMARY
ASSY
V
+34D
V
+5D
V
+3R3D
V
+1R2D
V
+15A
V
-15A
V
+5A
V
+3R3A
Monitoring
V
DET
RELAY_CO
N
T
V
+11E_U
N
REG
V
+3R3E
STBY_LED
Flashing when
an error occurs
TRA
N
S
ASSY
SEC/HP
ASSY
LDO
IC1401
Always output during power-on
Voltage-Monitoring Circuit
Product behavior when an error is generated
Diagnostic procedure
