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
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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
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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.
1
wear ribs (2 on underside)
2
bumps
3
slider
4
spring
5
bottom case
6
latch housing (2)
7
latch buttons (2)
8
location of snap tabs (2)

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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
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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
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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
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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)
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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.
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.

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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
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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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1
cam screw
2
perpendicular screwdriver
3
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
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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.
1
display
2
hinge cover
3
M2.5 x 6-mm screws (3)
4
bottom case
5
display flex cable

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1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Use a nonmarring plastic scribe to loosen the hinge cover at the back and at each side of the computer.
3. Open the computer and use the scribe to pry between the key and the hinge cover until the hinge cover pops off.
4. Open the display and lift off the hinge cover.
Display Assembly
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1. Remove the hinge cover.
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1
hinge cover
1
M2.5 x 6-mm screws (2)
NOTICE: Remove the display flex cable before you remove the display assembly.

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2. Remove the M2.5 x 6-mm flex-cable strain relief screw, and then use the pull loop to remove the display flex cable from the graphics card.
3. Open the display and, from the back of the computer, remove the two M2.5 x 6-mm screws labeled "circle D" that secure the display assembly to the
bottom case.
4. With the display in an upright position, lift the display assembly from the bottom case.
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1
M2.5 x 6-mm screw
2
strain relief
3
display flex cable
4
pull loop
NOTICE: When reconnecting the flex cable, press down on both ends of the connector, not in the middle. Pressing the middle of the connector can
damage fragile components.

Display Bezel
1. Use a scribe to pry out the four rubber screw covers located across the top of the bezel.
2. Remove the four M2.5 x 4-mm screws located across the top of the bezel.
3. Use a scribe at the indentations to pry out the two plastic screw covers located at the bottom of the bezel.
4. Remove the two M2.5 x 4-mm screws located at the bottom of the bezel.
5. Separate the bezel from the top cover.
The bezel is secured to the top cover with plastic tabs around the sides. Use a plastic scribe to help separate the bezel from the top cover.
Display Panel
Removing the Display Panel
1. Remove the hinge cover.
2. Detach the display flex cable from the strain relief and the graphics card.
3. Remove the display bezel.
4. Remove the M2.5 x 4-mm screw that secures the plastic flex-cable mounting bracket to the top cover.
5. Remove the six M2 x 3-mm screws (three on each side) from the right and left sides of the panel.
6. Lift the display panel and flex cable out of the top cover.
7. Disconnect the flex cable from the two connectors (one ZIF and one standard connector) on the display panel.
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1
M2.5 x 4-mm screws (6)
8
M2 x 3-mm screws (6)
2
rubber screw covers (4)
9
top cover
3
display bezel
10
hinge cover
4
plastic tabs (6)
11
display flex cable
5
M2.5 x 4-mm screw
12
display panel
6
flex-cable mounting bracket
13
plastic screw covers (2)
7
display latch
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1
ZIF connector
2
standard connector

Replacing the Display Panel
1. Connect the flex cable to the two connectors on the back of the display panel.
2. Place the display panel in the top cover, taking care that the flex cable is in place and is not crushed or crimped.
3. Reinstall the M2.5 x 4-mm screw that secures the flex-cable mounting bracket to the top cover.
4. Starting on the left side, use a magnetic screwdriver to reinstall the six M2 x 3-mm screws that secure the display panel in the top cover.
5. Reinstall the M2.5 x 6-mm flex-cable strain relief screw, and reconnect the flex cable to the graphics card.
6. Reinstall the display bezel.
Display Latch
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1. Remove the hinge cover.
2. Detach the display flex cable from the strain relief and the graphics card.
3. Remove the display bezel.
4. Remove the display panel from the top cover.
5. Remove the display latch by disengaging the latch and captive spring.
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NOTE: Use a magnetic screwdriver to reassemble the display panel in the display.

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Fan
Dell™Latitude™C840ServiceManual
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Removing the Fan
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the system board.
3. Remove the three M2 x 4-mm screws from the fan.
4. Disconnect the two fan cables from the system board.
5. Pull the fan away from the back-panel bracket.
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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.
1
fan cables
2
M2 x 4-mm screws (3)
NOTICE: When reconnecting the fan cables, connect the shorter cable to the connector closest to the fan. Route both cables so that they will not be
pinched by the microprocessor thermal-cooling assembly.

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Hard Drive and Fixed Optical Drive
Dell™Latitude™C840ServiceManual
Hard Drive
Fixed Optical Drive
Hard Drive
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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.
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
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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.
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.
1
bottom of computer
2
M3 x 5-mm screw
3
hard drive door
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.

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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.
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1
captive screw
2
pull tab

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Keyboard
Dell™Latitude™C840ServiceManual
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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.
4. Use a nonmarring plastic scribe under the blank key to pry up the keyboard.
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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.
1
M2.5 x 20-mm screws (4)
NOTICE: Be careful when handling the keyboard. The keycaps are fragile, easily dislodged, and time-consuming to replace.

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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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7. Disconnect the keyboard cable and lay the keyboard aside.
Replacing the Keyboard
1. While bracing the keyboard upright on its left end, connect the keyboard cable to the keyboard interface connector on the system board.
1
blank key
2
keyboard
3
right side of computer
1
keyboard cable
2
keyboard interface
connector
3
system board
NOTICE: Position the keyboard/track-stick flex cable so that it is not pinched when you replace the keyboard in the bottom case.

2. Insert the metal tabs at the left end of the keyboard under the edge of the bottom case, and fit the keyboard into place.
3. Check that the keyboard is correctly installed. The keys should be flush with the left and right surfaces of the palm rest.
4. Turn the computer over and reinstall the four M2.5 x 20-mm screws. For extra stability, you can open the computer slightly and brace the keyboard
under each screw as you install the screw.
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