42114101 Rev.1
27 /
2.1.8 Alarm Circuit
(1)
AC Fuse open alarm
(a)
Head drive time alarm circuit
This circuit monitors the drive time using the HDALM signal interlocked with the
overdrive signal of each drive circuit.
If the drive time of any drive circuit exceeds the specified time, the drive fault alarm
circuit sends an ALM-N signal to turn on the Thyristor.
This cause the secondary coil (50V) of the transformer to be short-circuited, causing
an overcurrent to flow through the primary coil and making the AC fuse (transformer
assy) open.
(b)
Overvoltage detection
50V, 12V and 5V voltages are monitored, at overvoltage alarm circuit turn-on, the
ALM-N signal is transmitted to the thyristor, then the AC fuse (transformer assy)
opens.
(2)
Alarm processing when DC power is low.
50V is converted into the POWLEV signal (0V to +5V) by R753 and R524 and input into
the A/D port of the MPU to control the drive time and the print speed (pass number) of
the head.
(a)
Head drive time
The head drive time is lengthened to compensate for the amount of voltage drop by
monitoring the POWLEV signal once every 500
µ
sec. to control and maintain the
impact necessary for each printing pin at the fixed value.
(b)
Print speed
Voltage, +50V
Pass number
Print speed
38V or more
1 Pass
100%
25V to 37V
1 Pass
100~30%
25V or less
1 Pass
30%
+50V
R753
R524
POWLEV
(3)
FAN alarm
The MPU detects 5V on the FANALM signal even through the fan is driven.
5V
R515
FANALM-P
Summary of Contents for ML490 Series
Page 1: ...42114101 Rev 1 1 135 ML490 491 PRINTER Maintenance Manual ODA...
Page 2: ...42114101 Rev 1 2...
Page 38: ...42114101 Rev 1 38 Drive gear Ink tank Ribbon cartridge Figure 2 6...
Page 48: ...42114101 Rev 1 48 Change arm Change lever Platen Release cam Figure 2 13 REAR TOP BOTTOM...
Page 96: ...42114101 Rev 1 96 9 Carriage Assy NK2 10 SUS Bearing portion of guide roller EM 30L B...
Page 119: ...42114101 Rev 1 119 6 8 9 7 1 2 3 11 10 4 5 Figure B 2 Printer General Assy...
Page 124: ...42114101 Rev 1 124 9 12 11 1 13 3 7 1 14 5 6 7 2 10 8 Figure B 4 Carriage Assy...