Dell latitude c840 schematic

Dell Latitude C840 Service Manual

Dell™ Latitude™ C840 Service Manual

Before You Begin

Preparing to Work Inside the Computer
Recommended Tools
Computer Orientation

Screw Identification
System Components
Hard Drive and Fixed Optical Drive

Hard Drive

Fixed Optical Drive
System Upgrades

Memory Modules

Modem Daughter Card

Mini PCI Card
Keyboard
Display

Display Overview

Hinge Cover

Display Assembly

Display Bezel

Display Panel

Display Latch
Microprocessor Thermal-Cooling Assembly
Microprocessor Module
Video Graphics Board
Palm Rest
Reserve Battery
System Board
Battery and Module Bay Latches
Battery Charger Board
LED Board
Fan
RJ-11/RJ-45 Module
Pin Assignments for I/O Connectors

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Before You Begin: Dell Latitude C840 Service Manual

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Before You Begin

Dell™ Latitude™ C840 Service Manual

Preparing to Work Inside the Computer
Recommended Tools
Computer Orientation
Screw Identification

Preparing to Work Inside the Computer

CAUTION: Only a certified service technician should perform repairs on

your computer. Damage due to servicing that is not authorized by Dell
is not covered by your warrantly. Read and follow all safety instructions
in "Safety and EMC Instructions: Portable Computers" in your System
Information Guide.

NOTICE: To avoid damaging the computer, perform the following steps before

you begin working inside the computer.

1. Ensure that the work surface is flat and clean to prevent scratching the
computer cover.

2. Save any work in progress and exit all open programs.

3. Turn off the computer and all attached devices.

NOTE: Before turning off the computer, ensure that the computer is not in a

power-management mode.

4. Ensure that the computer is undocked.

5. Disconnect the computer from the electrical outlet.

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Before You Begin: Dell Latitude C840 Service Manual

6. To avoid possible damage to the system board, wait 10 to 20 seconds and then
disconnect any attached devices.

7. Disconnect all other external cables from the computer.

8. Remove any installed PC Cards or plastic blanks from the PC Card slot.

9. Close the display and turn the computer upside down on a flat work surface.

10. Remove the battery from the battery bay.

NOTICE: To avoid component damage, always remove any installed batteries

before you service the computer.

11. Remove any device installed in the module bay.

12. To dissipate static electricity while you work, periodically touch an unpainted
metal surface on the computer chassis.

13. Handle components and cards by their edges, and avoid touching pins and
contacts.

Recommended Tools

The procedures in this document require the following tools:

● #1 magnetized Phillips screwdriver

● Small flat-blade screwdriver

● Microprocessor extractor

● Nonmarring plastic scribe

● Flash BIOS update floppy disk or CD (provided when needed to upgrade the

BIOS)

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Before You Begin: Dell Latitude C840 Service Manual

Computer Orientation

Screw Identification

When you are removing and replacing components, photocopy the placemat as a tool
to lay out and keep track of the component screws. The placemat provides the
number of screws and the sizes.

Screw Identification

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Before You Begin: Dell Latitude C840 Service Manual

NOTICE: When reinstalling a screw, you must use a screw of the correct

diameter and length. Ensure that the screw is properly aligned with its
corresponding hole, and avoid overtightening.

Hard-Drive Door Security:

M3 x 5 mm (1 each)

Keyboard to Bottom Case:

M2.5 x 20 mm (4 each; one in
memory door and one in Mini
PCI door)

Display to Bottom
Case:

M2.5 x 6 mm (3
each; 2 at back of
computer; 1 at
display flex-cable
strain relief)

Display Bezel:

Rubber screw covers (4 each)

Plastic screw covers (2 each)

M2.5 x 4 mm (6 each)

Display Panel to Display
Mounting Bracket:

M2 x 3 mm (6 each)

Flex-Cable Mounting Bracket to
Top Cover:

Video Graphics
Board:

M2.5 x 8 (3 each)

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Before You Begin: Dell Latitude C840 Service Manual

M2.5 x 4 mm (1 each)

Palm Rest to
Bottom Case:

M2.5 x 20 mm (9 each)

Palm Rest Bracket:
M2.5 x 4 mm (4 each)

System Board:

M2.5 x 4 mm captive washer
(3 each)

M2.5 x 20 mm (1 each)

LED Board:

M2 x 4 mm (2 each)

Fan:

M2 x 4 mm (3 each)

Memory Module/Modem Cover:

M2.5 x 20 mm (1 each)

Modem Daughter
Card:

M2 x 3 mm (1 each)

Mini PCI Card:

M2.5 x 20 mm (1 each)

Back to Contents Page

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System Components: Dell Latitude C840 Service Manual

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System Components

Dell™ Latitude™ C840 Service Manual

NOTICE: Unless otherwise noted, each procedure in this document assumes

that a part can be replaced by performing the removal procedure in reverse
order.

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System Components: Dell Latitude C840 Service Manual

1 display assembly 7 main battery
2 hinge cover 8 device in module

bay

3 microprocessor thermal-

cooling assembly

9 fixed optical drive

4 system board 10 palm rest
5 hard drive 11 keyboard
6 bottom case

Back to Contents Page

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Hard Drive and Fixed Optical Drive: Dell Latitude C840 Service Manual

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Hard Drive and Fixed Optical Drive

Dell™ Latitude™ C840 Service Manual

Hard Drive
Fixed Optical Drive

NOTICE: Only a certified service technician should perform repairs on your

computer. Damage due to servicing that is not authorized by Dell is not covered
by your warranty.

Hard Drive

NOTICE: Disconnect the computer and attached devices from the electrical

outlet and remove any installed batteries.

NOTICE: To avoid ESD, ground yourself by using a wrist grounding strap or by

periodically touching unpainted metal on the computer.

NOTICE: The hard drive is very sensitive to shock. Handle the drive by its

edges (do not squeeze the top of the case), and avoid dropping it.

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Hard Drive and Fixed Optical Drive: Dell Latitude C840 Service Manual

1 bottom of computer
2 M3 x 5-mm screw
3 hard drive door

Removing the Hard Drive

1. Follow the instructions in "Preparing to Work Inside the Computer."

2. Remove the M3 x 5-mm screw.

3. Pull the hard drive out.

Replacing the Hard Drive

1. Push the hard drive into the drive bay until the drive door is flush with the
computer case.

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Hard Drive and Fixed Optical Drive: Dell Latitude C840 Service Manual

2. Push down on the drive until it snaps into place.

3. Replace the M3 x 5-mm screw in the hard drive door.

Fixed Optical Drive

NOTICE: Disconnect the computer and attached devices from the electrical

outlet and remove any installed batteries.

NOTICE: To avoid ESD, ground yourself by using a wrist grounding strap or by

periodically touching unpainted metal on the computer.

1 captive screw
2 pull tab

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Hard Drive and Fixed Optical Drive: Dell Latitude C840 Service Manual

Removing the Fixed Optical Drive

1. Follow the instructions in "Preparing to Work Inside the Computer."

2. Loosen the captive screw on the bottom of the computer.

3. Turn the computer over (to keep the captive screw from interfering with the pull
tab) and pull out the pull tab.

4. Use the pull tab to remove the fixed optical drive.

Back to Contents Page

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System Upgrades: Dell Latitude C840 Service Manual

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System Upgrades

Dell™ Latitude™ C840 Service Manual

Memory Modules
Modem Daughter Card
Mini PCI Card

Memory Modules

NOTICE: Disconnect the computer and any attached devices from electrical

outlets and remove any installed batteries.

NOTICE: To avoid ESD, ground yourself by using a wrist grounding strap or by

periodically touching unpainted metal on the computer.

Removing the Memory Module/Modem Cover

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System Upgrades: Dell Latitude C840 Service Manual

1 M2.5 x 20-mm screw

1. Follow the instructions in "

Preparing to Work Inside the Computer."

2. Remove the M2.5 x 20-mm screw from the memory module/modem cover.

3. Disengage the metal tabs at the opposite end of the cover.

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System Upgrades: Dell Latitude C840 Service Manual

1 DIMM B
2 memory module sockets

(2)
3 DIMM A socket
4 modem daughter card
5 metal tabs (2 per

socket)

Removing the Memory Modules

1. Remove the memory module/modem cover.

2. To release a memory module from its socket, spread apart the tabs at each side
of the module until the module pops up slightly.

3. Lift the memory module out of its socket.

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System Upgrades: Dell Latitude C840 Service Manual

Replacing the Memory Modules

1. If you only have one memory module, install it in the socket labeled "DIMM A."
Install a second memory module in the socket labeled "DIMM B."

NOTE: Memory modules are keyed to fit into their sockets in only one direction.

2. Insert the memory-module edge connector into the socket slot at a 45-degree
angle and press the module firmly into the slot.

3. Pivot the module down until it clicks into place. If you do not hear a click,
remove the module and reinstall it.

4. Insert the metal tabs on the memory module/modem cover into the bottom
case, rotate the cover down, and replace the M2.5 x 20-mm screw.

Modem Daughter Card

Removing the Modem Daughter Card

NOTICE: Disconnect the computer and any attached devices from electrical

outlets and remove any installed batteries.

NOTICE: To avoid ESD, ground yourself by using a wrist grounding strap or by

periodically touching unpainted metal on the computer.

1. Follow the instructions in "

Preparing to Work Inside the Computer."

2. Turn the computer over and remove the

memory module/modem cover.

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System Upgrades: Dell Latitude C840 Service Manual

1 modem daughter card
2 M2 x 3-mm screw

3. Remove the M2 x 3-mm screw that secures the modem daughter card to the
system board.

4. Use the pull tab to pull the modem daughter card straight up out of its
connector.

NOTICE: Do not pull on the modem cable. Pull the connector on the end of the

cable to disconnect the cable.

5. Disconnect the modem cable from the modem daughter card.

Replacing the Modem Daughter Card

NOTICE: The cable connectors are keyed for correct insertion. Do not force the

connections.

1. Connect the modem cable to the modem daughter card.

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System Upgrades: Dell Latitude C840 Service Manual

2. Use the screw and boss holes at opposite corners of the modem daughter card
to align the card, and press the card into its connector on the system board.

3. Install the M2 x 3-mm screw that secures the card to the system board.

4. Replace the memory module/modem cover.

Mini PCI Card

You must remove the optional Mini PCI wireless modem (if installed) before the
system board can be removed. A wireless modem card must be connected to the
internal antenna of the computer.

NOTICE: Disconnect the computer and attached devices from electrical outlets

and remove any installed batteries.

NOTICE: To avoid ESD, ground yourself by using a wrist grounding strap or by

periodically touching unpainted metal on the computer.

Mini PCI Card Cover

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System Upgrades: Dell Latitude C840 Service Manual

1 M2.5 x 20-mm screw

Removing the Mini PCI Card

1. Follow the instructions in "Preparing to Work Inside the Computer."

2. Remove the M2.5 x 20-mm screw and then remove the Mini PCI card cover.

3. To release the Mini PCI card, spread the metal securing tabs until the card pops
up slightly.

4. Disconnect the card from the internal antenna.

5. Lift out the card and disconnect any attached cables.

Replacing the Mini PCI Card

1. Align the Mini PCI card with the socket at a 45-degree angle, and press the Mini
PCI card into the socket.

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2. Connect the internal-antenna cable to the primary-antenna connector on the
card.

NOTICE: The connectors are keyed for correct insertion; do not force the

connections.

1 internal-antenna cable
2 primary-antenna

connector on card

3. Pivot the Mini PCI card down until it clicks into place.

4. Replace the Mini PCI card cover and the M2.5 x 20-mm screw.

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Back to Contents Page

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Keyboard: Dell Latitude C840 Service Manual

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Keyboard

Dell™ Latitude™ C840 Service Manual

NOTICE: Disconnect the computer and attached devices from electrical outlets

and remove any installed batteries.

NOTICE: To avoid ESD, ground yourself by using a wrist grounding strap or by

periodically touching unpainted metal on the computer.

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Keyboard: Dell Latitude C840 Service Manual

1 M2.5 x 20-mm screws

(4)

Removing the Keyboard

1. Follow the instructions in "Preparing to Work Inside the Computer."

2. Turn the computer over and remove the four M2.5 x 20-mm screws (three
labeled "circle K" and one labeled "circle K/M").

3. Turn the computer over and open the display.

NOTICE: Be careful when handling the keyboard. The keycaps are fragile,

easily dislodged, and time-consuming to replace.

4. Use a nonmarring plastic scribe under the blank key to pry up the keyboard.

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Keyboard: Dell Latitude C840 Service Manual

1 blank key
2 keyboard
3 right side of computer

5. Lift the right end of the keyboard and slide it slightly toward the right side of the
computer to disengage the tabs at the left end.

6. Pivot the keyboard and balance it upright on the left side of the computer.

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