Apple 250 manual Inverter/Speaker Board, MB Hard Disk Drive

C H A P T E R 2

Hardware Modifications

Inverter/Speaker Board

▲W AR N I N G

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

This section describes the 200 MB hard disk drive. It includes the following information about the drive:

■environmental specifications

■housing requirements

■interface requirements

Inverter/Speaker Board 7