CHAPTER 2
Hardware Modifications
Inverter/Speaker Board
7
Inverter/Speaker Board 2▲
WARNING
You should not open or modify any of the circuitry associated with the
inverter/speaker board.
The PowerBook Duo 250 active-matrix display is assembled into the
clamshell housing in a clean room environment. Opening up the
equipment in any other environment could cause damage to the unit.
The high-voltage inverter/speaker board may pose a risk if you are
handling the board.
The LCD display is susceptible to damage from electrostatic
discharge (ESD).
▲
The inverter/speaker board is located in the clamshell housing, directly under the LCD.
It interfaces between the basic CPU and the active-matrix LCD display and performs the
following basic functions for the PowerBook Duo 250 computer:
■
It converts the DC power supplied by the computer’s battery to the AC power
required to drive the cold cathode fluorescent lamp (CCFL), that provides the back-
lighting for the active-matrix LCD display. Typical CCFL drive power is 400 VRMS
(voltage root mean square) at 3mA, with maximum output of 2000 V peak to peak
at 6 mA.
■
It provides pass-through circuitry for the data and timing signals, supplied by the GSC
to the LCD display, and for the +5 V from the power supply.
■
It converts the DC voltage supplied by the computer’s battery to the +13 VDC level
required for the LCD bias/contrast voltage, which is typically +13 V at 30 mA.
The board is also used in basic PowerBook Duo computers to convert the battery-
supplied DC power to the +28V DC level for the LCD bias/contrast voltage required
by the film super-twist nematic LCD display.
200 MB Hard Disk Drive 2 This section describes the 200 MB hard disk drive. It includes the following information
about the drive:
■
environmental specifications
■
housing requirements
■
interface requirements