Dell Latitude C840 User 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 
Notes, Notices, and Cautions 
Information in this document is subject to change without notice. 
©2002DellComputerCorporation.Allrightsreserved. 
Reproduction in any manner whatsoever without the written permission of Dell Computer Corporation is strictly forbidden. 
Trademarks used in this text: Dell, the DELL logo, and Latitude are trademarks of Dell Computer Corporation; Intel is a registered trademark of Intel Corporation; Microsoft and 
Windows are registered trademarks of Microsoft Corporation. 
Other trademarks and trade names may be used in this document to refer to either the entities claiming the marks and names or their products. Dell Computer Corporation 
disclaims any proprietary interest in trademarks and trade names other than its own. 
This product incorporates copyright protection technology that is protected by method claims of certain U.S. patents and other intellectual property rights owned by Macrovision 
Corporation and other rights owners. Use of this copyright protection technology must be authorized by Macrovision Corporation, and is intended for home and other limited 
viewing uses only unless otherwise authorized by Macrovision Corporation. Reverse engineering or disassembly is prohibited. 
February2002Rev.A00 
NOTE: A NOTE indicates important information that helps you make better use of your computer. 
NOTICE: A NOTICE indicates either potential damage to hardware or loss of data and tells you how to avoid the problem. 
 
CAUTION: A CAUTION indicates a potential for property damage, personal injury, or death. 

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Battery Charger Board

Dell™Latitude™C840ServiceManual



Removing the Battery Charger Board

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

2. Remove the keyboard.

3. Remove the hinge cover.

4. Remove the display assembly.

5. Remove the palm rest.

6. Remove the video graphics board.

7. Lift the battery charger board out of the system board connector.

Replacing the Battery Charger Board

Align the screw holes on the battery charger board with the screw holes on the bottom case, and then press the battery charger board down into its

connector.

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

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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Battery and Module Bay Latches

Dell™Latitude™C840ServiceManual



Removing and Replacing the Battery and Module Bay Latches

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

2. Remove the keyboard.

3. Remove the hinge cover.

4. Remove the display assembly.

5. Remove the palm rest.

6. Remove a latch button from the bottom case by squeezing the snap tabs in the center of the latch.

Tape over or hold down the upper latch assembly (spring and slider) to hold the assembly in place. Apply downward pressure to the snap tabs while

squeezing them together (tweezers work well) to eject the latch button from the underside of the bottom case without loosening the upper latch

assembly. If the upper latch assembly does come loose:

a. Slide the spring onto the slider, and reinstall both pieces in the latch housing on the inside of the bottom case.

b. Ensure that the slider is inserted so that the side with the two bumps is facing the back of the bottom case, and the surface with the wear ribs

lies against the upper surface of the bottom case.

7. Hold the upper latch assembly in place while you snap the new latch button in from underneath the bottom case, making certain the snap tabs are fully

engaged in the slider.

Ensure that the newly installed latch assembly moves smoothly and freely when pushed and released.

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.

wear ribs (2 on underside)

bumps

slider

spring

bottom case

latch housing (2)

latch buttons (2)

location of snap tabs (2)

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

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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

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.

4. Ensure that the computer is undocked.

5. Disconnect the computer from the electrical outlet.

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.

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:

l#1 magnetized Phillips screwdriver

lSmall flat-blade screwdriver

lMicroprocessor extractor

lNonmarring plastic scribe

lFlash BIOS update floppy disk or CD (provided when needed to upgrade the BIOS)

Computer Orientation



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.

NOTE: Before turning off the computer, ensure that the computer is not in a power-management mode.

NOTICE: To avoid component damage, always remove any installed batteries before you service the computer.

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



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:

M2.5 x 4 mm (1 each)

Video Graphics Board:

M2.5 x 8 (3 each)

Palm Rest to

Bottom Case:

M2.5 x 20 mm (9 each)

System Board:

M2.5 x 4 mm captive washer

(3 each)

LED Board:

M2 x 4 mm (2 each)

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Palm Rest Bracket:

M2.5 x 4 mm (4 each)

M2.5 x 20 mm (1 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)



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Microprocessor Module

Dell™Latitude™C840ServiceManual



Removing the Microprocessor Module

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

2. Remove the keyboard.

3. Remove the hinge cover.

4. Remove the microprocessor thermal-cooling assembly.

5. Remove the microprocessor module.

a. Loosen the cam screw that secures the microprocessor module. The location of the screw and the rotation direction may vary with the socket

manufacturer; look for small icons indicating open and locked positions.

Microprocessor Cam Screw (Example)



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.

NOTICE: To ensure maximum cooling for the microprocessor, do not touch the heat transfer areas on the microprocessor thermal-cooling assembly. The

oils in your skin reduce the heat transfer capability of the thermal pads.

NOTICE: When removing the microprocessor module, pull the module straight up. Do not bend the pins.

NOTICE: To avoid damage to the microprocessor, hold the screwdriver so that it is perpendicular to the microprocessor when loosening the cam screw

(see "Microprocessor Cam Screw").

NOTICE: Hold the microprocessor down while turning the cam screw to prevent intermittent contact between the cam screw and microprocessor.



b. Use the microprocessor extraction tool to remove the microprocessor module.

Replacing the Microprocessor Module

1. Align the pin-1 triangle on the microprocessor with the pin-1 triangle in the socket, insert the microprocessor into the socket, and move the

microprocessor around slightly until you feel it settle into the socket.

When the microprocessor module is correctly seated, all four corners are aligned to the same height. If one or more corners of the module are higher

than the others, the module is not seated correctly.

2. Tighten the cam screw.

3. Replace the microprocessor thermal-cooling assembly.

Closing the Microprocessor Retaining Clip



4. Close the microprocessor retaining clip.

5. To latch the clip, insert a flat-blade scribe into the latch mechanism and pivot the top of the scribe away from the clip.

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

cam screw

perpendicular screwdriver

processor die (do not

touch)

NOTICE: If you received a flash BIOS update floppy disk or CD with the replacement microprocessor, you must update the BIOS after replacing the

microprocessor module.

NOTICE: Proper seating of the microprocessor module does not require force.

NOTICE: A microprocessor module that is not properly seated can result in an intermittent connection and subsequent failures.

NOTICE: Hold the microprocessor down while turning the cam screw to prevent intermittent contact between the cam screw and microprocessor (see

"Microprocessor Cam Screw").

NOTICE: Do not over-or undertighten the screw. Tighten the screw until the screw indicator points to the "closed" or "locked" indicator on the socket.

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Display

Dell™Latitude™C840ServiceManual

Display Overview

Hinge Cover

Display Assembly

Display Bezel

Display Panel

Display Latch

Display Overview



Hinge Cover

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.

display

hinge cover

M2.5 x 6-mm screws (3)

bottom case

display flex cable

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