Chapter 1: Product Overview 1-21
Contrast control is set by software, using a digital potentiometer on the
Processor Board. The terminal does not have a user-accessible contrast
adjustment. Software can set a default value after reading the Panel ID.
Display contrast changes with temperature.
LCD Adapter Board
The signals from the LCD header on the Processor Board are brought
to the LCD on a harness. Since there are multiple pin configurations
and connector types being used on the LCD, a small adapter board is
used to receive the LCD harness and map the signals into the correct
pinout for the LCD panel. This board has a connector that plugs
directly into the LCD panel.
LCD Backlight Inverter Module
An Inverter Board supplies power for the LCD Backlight, which is a
separate module in the terminal. The inverter has a connector that
receives power, ground, and a Backlight dimming signal from the
Processor Board. The inverter generates the high voltage necessary to
start and run dual CCFL Backlights.
A fuse located on the Inverter Board protects power to the inverter.
This fuse protects the system from damage in the event of a Backlight
or Inverter Board fault. The fuse is not field replaceable; if it blows, the
safety characteristics of one or more components on the Inverter Board
may have been compromised and the Inverter Board should be
replaced.
If one or both Backlight tubes become disconnected or otherwise open-
circuited, protection circuitry shuts down the inverter. This avoids
over-powering a single tube and also protects against high voltage
shorting.
