4-8
Chadwick-Helmuth A Business Unit of Honeywell International, Inc.
Chapter 4
- System Theory of Operation
4.2.1.1.3 Heater/EL Control Board (Figure 4-4)
The heater/EL control board provides power and control of LCD screen heater and EL lamps used
behind the keypanel and LCD. The board contains a power supply filter, a display heater controller,
and an EL controller.
Figure 4-4. Heater/EL Control Board
a.
Power Supply Filter. The 28 VDC input power is applied to the power supply filter from
the external power connector. The input power passes through a 2.5 Ampere fuse, a diode
bridge, and a filter. Voltages greater than 60 to 85 Volts are shorted to ground by a surge
protector which causes the fuse to open. The diode bridge su27 VDC with the
correct polarity if the input +28 VDC polarity is reversed. The thermal cutoff switch shuts
off power to the display heater and EL lamps when the internal temperature is above
+65°C. This protects the EL lamps whose life span is decreased when operated at high
temperature. It also prevents the display heater from operating at high temperatures, in the
event of a controller failure.
2.5A
FUSE
+28 VDC
DIODE
BRIDGE
FILTER
THERMAL
CUTOFF
SWITCH
+27 VDC
POWER SUPPLY FILTER
DISPLAY HEATER
+27 VDC
VOLTAGE
REGULATOR
+12V
HEATER
CONTROLLER
HEATER
EL CONTROLLER
+27 VDC
VARIABLE
VOLTAGE
REGULATOR
EL
INVERTER
10K
BRIGHTNESS
ADJUSTMENT
EL LAMPS
(KEYPANEL)
EL LAMPS
(LCD DISPLAY)
FILE: FIG4-4.DRW
Содержание Chadwick-Helmuth 8500C
Страница 12: ...xii Chadwick Helmuth A Business Unit of Honeywell International Inc List of Tables ...
Страница 17: ...System Physical Description 8500C 8500C System Maintenance Manual 1 5 Figure 1 3 System Cables ...
Страница 44: ...4 14 Chadwick Helmuth A Business Unit of Honeywell International Inc Chapter 4 System Theory of Operation ...
Страница 97: ...Disassembly 8500C 8500C System Maintenance Manual 5 53 Figure 5 17 Balancer Analyzer Assembly Parts Breakdown ...
Страница 103: ...Disassembly 8500C 8500C System Maintenance Manual 5 59 Figure 5 19 8500C C Harness Assembly Sheet 1 of 2 ...
Страница 105: ...Disassembly 8500C 8500C System Maintenance Manual 5 61 Figure 5 19 8500C C Harness Assembly Sheet 2 of 2 ...
Страница 109: ...Disassembly 8500C 8500C System Maintenance Manual 5 65 Figure 5 21 8520C Harness Assemblies Sheet 1 of 2 ...
Страница 111: ...Disassembly 8500C 8500C System Maintenance Manual 5 67 Figure 5 21 8520C Harness Assemblies Sheet 2 of 2 ...
Страница 122: ...5 78 Chadwick Helmuth A Business Unit of Honeywell International Inc Chapter 5 Maintenance And Repair ...
Страница 154: ...A 32 Chadwick Helmuth A Business Unit of Honeywell International Inc Appendix A 8520C 36 Signal Selector ...
Страница 179: ...Maintenance and Repair 8500C 8500C System Maintenance Manual D 21 Figure D 12 Wiring Diagram 8520CS Sheet 1 of 2 ...
Страница 181: ...Maintenance and Repair 8500C 8500C System Maintenance Manual D 23 Figure D 12 Wiring Diagram 8520CS Sheet 2 of 2 ...