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Dell Latitude C840 Service Manual
DellTM LatitudeTM 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
DellTM LatitudeTM 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:
q #1 magnetized Phillips screwdriver
q Small flat-blade screwdriver
q Microprocessor extractor
q Nonmarring plastic scribe
q 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: Keyboard to Bottom Case: Display to Bottom
Case:
M3 x 5 mm (1 each) M2.5 x 20 mm (4 each; one in
memory door and one in Mini M2.5 x 6 mm (3
PCI door) each; 2 at back of
computer; 1 at
display flex-cable
strain relief)
Display Bezel: Display Panel to Display Video Graphics
Mounting Bracket: Board:
Rubber screw covers (4 each)
M2 x 3 mm (6 each) M2.5 x 8 (3 each)
Plastic screw covers (2 each)
M2.5 x 4 mm (6 each)
Flex-Cable Mounting Bracket to
Top Cover:
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Before You Begin: Dell Latitude C840 Service Manual
M2.5 x 4 mm (1 each)
Palm Rest to System Board: LED Board:
Bottom Case:
M2.5 x 4 mm captive washer M2 x 4 mm (2 each)
M2.5 x 20 mm (9 each) (3 each)
Palm Rest Bracket:
M2.5 x 4 mm (4 each) M2.5 x 20 mm (1 each)
Fan: Memory Module/Modem Cover: Modem Daughter
Card:
M2 x 4 mm (3 each) M2.5 x 20 mm (1 each)
M2 x 3 mm (1 each)
Mini PCI Card:
M2.5 x 20 mm (1 each)
Back to Contents Page
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Before You Begin: Dell Latitude C840 Service Manual
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System Components: Dell Latitude C840 Service Manual
Back to Contents Page
System Components
DellTM LatitudeTM 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- 9 fixed optical drive
cooling assembly
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
Back to Contents Page
Hard Drive and Fixed Optical Drive
DellTM LatitudeTM 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
DellTM LatitudeTM 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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System Upgrades: Dell Latitude C840 Service Manual
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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System Upgrades: Dell Latitude C840 Service Manual
Back to Contents Page
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Keyboard: Dell Latitude C840 Service Manual
Back to Contents Page
Keyboard
DellTM LatitudeTM 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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Keyboard: Dell Latitude C840 Service Manual
1 keyboard cable
2 keyboard interface
connector
3 system board
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.
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Keyboard: Dell Latitude C840 Service Manual
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.
Back to Contents Page
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Display: Dell Latitude C840 Service Manual
Back to Contents Page
Display
DellTM LatitudeTM C840 Service Manual
Display Overview
Hinge Cover
Display Assembly
Display Bezel
Display Panel
Display Latch
Display Overview
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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Display: Dell Latitude C840 Service Manual
1 display
2 hinge cover
3 M2.5 x 6-mm screws (3)
4 bottom case
5 display flex cable
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Display: Dell Latitude C840 Service Manual
Hinge Cover
1 hinge cover
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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Display: Dell Latitude C840 Service Manual
1 M2.5 x 6-mm screws (2)
1. Remove the hinge cover.
NOTICE: Remove the display flex cable before you remove the display
assembly.
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Display: Dell Latitude C840 Service Manual
1 M2.5 x 6-mm screw
2 strain relief
3 display flex cable
4 pull loop
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.
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.
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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Display: Dell Latitude C840 Service Manual
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Display: Dell Latitude C840 Service Manual
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 13 plastic screw covers
bracket (2)
7 display latch
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.
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Display: Dell Latitude C840 Service Manual
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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Display: Dell Latitude C840 Service Manual
1 ZIF connector
2 standard connector
Replacing the Display Panel
NOTE: Use a magnetic screwdriver to reassemble the display panel in the
display.
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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Display: Dell Latitude C840 Service Manual
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.
Back to Contents Page
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Microprocessor Thermal-Cooling Assembly: Dell Latitude C840 Service Manual
Back to Contents Page
Microprocessor Thermal-Cooling
Assembly
DellTM LatitudeTM 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.
1 microprocessor thermal-
cooling assembly
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Microprocessor Thermal-Cooling Assembly: Dell Latitude C840 Service Manual
2 microprocessor retaining
clip
Removing the Microprocessor Thermal-Cooling
Assembly
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the keyboard.
3. Remove the hinge cover.
4. Insert a non-marring plastic scribe into the latch mechanism at the left side of
the microprocessor retaining clip. Pry open the clip by pivoting the top of the
screwdriver toward the right side of the computer.
1 microprocessor thermal-
cooling assembly
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Microprocessor Thermal-Cooling Assembly: Dell Latitude C840 Service Manual
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.
5. Lift out the thermal-cooling assembly.
Back to Contents Page
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Microprocessor Module: Dell Latitude C840 Service Manual
Back to Contents Page
Microprocessor Module
DellTM LatitudeTM 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.
Removing the Microprocessor Module
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the keyboard.
3. Remove the hinge cover.
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Microprocessor Module: Dell Latitude C840 Service Manual
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.
4. Remove the microprocessor thermal-cooling assembly.
NOTICE: When removing the microprocessor module, pull the module straight
up. Do not bend the pins.
5. Remove the microprocessor module.
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").
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: Hold the microprocessor down while turning the cam screw to prevent
intermittent contact between the cam screw and microprocessor.
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Microprocessor Module: Dell Latitude C840 Service Manual
1 cam screw
2 perpendicular
screwdriver
3 processor die (do not
touch)
b. Use the microprocessor extraction tool to remove the microprocessor
module.
Replacing the Microprocessor Module
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.
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Microprocessor Module: Dell Latitude C840 Service Manual
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.
NOTICE: Hold the microprocessor down while turning the cam screw to prevent
intermittent contact between the cam screw and microprocessor (see
"Microprocessor Cam Screw").
2. Tighten the 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.
3. Replace the microprocessor thermal-cooling assembly.
Closing the Microprocessor Retaining Clip
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Microprocessor Module: Dell Latitude C840 Service Manual
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.
Back to Contents Page
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Video Graphics Board: Dell Latitude C840 Service Manual
Back to Contents Page
Video Graphics Board
DellTM LatitudeTM 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.
1 M2.5 x 8-mm screws (3)
Removing the Video Graphics Board
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the keyboard.
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Video Graphics Board: Dell Latitude C840 Service Manual
3. Remove the hinge cover.
NOTICE: The video graphics board may have a metallic or cardboard-like EMI
shield attached to the top. If present, the EMI shield is removed with the board.
Do not reuse the EMI shield on the replacement video board. Newer versions of
the board may not require the shield; if a shield is required, it is already
attached to the replacement board.
4. Detach the display flex cable from the graphics card.
5. Remove the three M2.5 x 8-mm screws that secure the video graphics board.
6. Separate the video graphics board from the system board connector.
Replacing the Video Graphics Board
1. Align the three screw holes and press down firmly on the word "Dell" to seat the
board in its connector.
NOTICE: Ensure that the board is correctly and firmly seated before continuing.
Failure to do so will cause intermittent video failures.
2. Replace the three M2.5 x 8-mm screws.
Back to Contents Page
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Palm Rest: Dell Latitude C840 Service Manual
Back to Contents Page
Palm Rest
DellTM LatitudeTM 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.
1 pull loop
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Palm Rest: Dell Latitude C840 Service Manual
NOTICE: The reserve battery provides power to the computer's time RTC and
NVRAM when the computer is turned off. Removing the palm rest disconnects
the reserve battery and causes the computer to lose the date and time
information as well as all user-specified parameters in NVRAM. If possible, copy
the information before you disconnect the reserve battery.
Removing the Palm Rest
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the hard drive and the fixed optical drive.
3. Remove the keyboard.
4. Remove the hinge cover.
5. Remove the display assembly.
NOTICE: To avoid damaging the palm rest, you must first remove the display
assembly.
6. Turn the computer over.
7. Remove the nine M2.5 x 20-mm screws (labeled "circle P") that secure the palm
rest to the computer.
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Palm Rest: Dell Latitude C840 Service Manual
1 M2.5 x 20-mm screws
(9)
8. Turn the computer over.
9. Use the pull loop to disconnect the palm-rest flex cable from the touch-pad
connector on the system board.
10. On the left and right sides of the palm rest, use a flat-blade scribe between the
palm rest and the bottom case of the computer to separate the snaps that
secure the palm rest to the bottom case.
11. Lift out the palm rest.
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Palm Rest: Dell Latitude C840 Service Manual
Replacing the Palm Rest
When replacing the palm rest screws, install the two screws at the back corners of the
computer first to help align the palm rest correctly.
Back to Contents Page
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Reserve Battery: Dell Latitude C840 Service Manual
Back to Contents Page
Reserve Battery
DellTM LatitudeTM 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.
1 palm rest bracket
2 reserve battery
3 reserve battery cable
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Reserve Battery: Dell Latitude C840 Service Manual
NOTICE: The reserve battery provides power to the computer's RTC and
NVRAM when the computer is turned off. Removing the battery causes the
computer to lose the date and time information as well as all user-specified
parameters in NVRAM. If possible, copy the information before you remove the
reserve battery.
Removing the Reserve Battery
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. On the underside of the palm rest, disconnect the palm-rest flex cable from the
ZIF connector.
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Reserve Battery: Dell Latitude C840 Service Manual
1 M2.5 x 4-mm screws (4)
2 palm rest bracket
3 palm-rest flex cable
7. Remove the four M2.5 x 4-mm screws that secure the palm rest bracket.
8. While supporting the palm-rest flex cable, lift out the palm rest bracket and turn
it over.
9. Disconnect the reserve battery cable.
10. Remove the reserve battery:
a. Pry the reserve battery free from the metal palm rest bracket.
b. Remove the foam-pad remnants from the palm rest bracket.
Replacing the Reserve Battery
1. Seat the reserve battery and press it into place.
2. Connect the reserve battery cable.
3. Place the palm rest bracket loosely in the palm rest, and connect the palm-rest
flex cable to the ZIF connector.
4. Replace the four M2.5 x 4-mm screws that secure the palm rest bracket to the
palm rest.
Back to Contents Page
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System Board: Dell Latitude C840 Service Manual
Back to Contents Page
System Board
DellTM LatitudeTM 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.
1 M2.5 x 4-mm captive-
washer screws (3)
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System Board: Dell Latitude C840 Service Manual
2 system board
3 network connector
4 modem connector
5 network cable cover
6 M2.5 x 20-mm screw
The BIOS chip on the system board contains the service tag sequence, which is also
visible on a bar code label on the bottom of the computer.
The replacement kit for the system board includes a floppy disk or CD that provides a
utility for transferring the service tag sequence to the replacement system board.
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.
Removing the System Board
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the hard drive and the fixed optical drive.
3. Remove any installed Mini PCI Cards.
4. If migrating the memory, remove all installed memory modules.
5. Remove (if migrating) or disconnect the modem daughter card.
6. Remove the keyboard.
7. Remove the hinge cover.
8. Remove the display assembly.
9. Remove the palm rest.
10. Remove the video graphics board.
11. Remove the microprocessor thermal-cooling assembly.
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System Board: Dell Latitude C840 Service Manual
12. If migrating the microprocessor, remove the microprocessor module.
13. Separate the network cable from the system board:
a. First remove the network cable cover: Insert a narrow plastic scribe or
small screwdriver just barely into the slot that faces the back of the
computer (do not insert the scribe far enough to catch on the wires
inside), press down on the cover lightly to secure it, and pry upward to
release the cover.
1 network cable cover
b. Disconnect the network cable. Do not pull on the cable wires. Instead, pry
up the outer corner of the upper connector until the connectors start to
separate.
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System Board: Dell Latitude C840 Service Manual
1 outer corner of upper
connector
2 network cable
14. Remove the three M2.5 x 4-mm captive-washer screws from the system board.
15. Remove the M2.5 x 20-mm screw from the center of the LED board.
16. Lift the front of the system board and work it out of the back panel.
If necessary to help release the system board, pull outward on the top of the
plastic near the back left corner of the bottom case (see the small arrow at the far
left in the following figure).
System Board
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System Board: Dell Latitude C840 Service Manual
Back to Contents Page
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Battery and Module Bay Latches: Dell Latitude C840 Service Manual
Back to Contents Page
Battery and Module Bay Latches
DellTM LatitudeTM 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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Battery and Module Bay Latches: Dell Latitude C840 Service Manual
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)
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.
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Battery and Module Bay Latches: Dell Latitude C840 Service Manual
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.
Back to Contents Page
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Battery Charger Board: Dell Latitude C840 Service Manual
Back to Contents Page
Battery Charger Board
DellTM LatitudeTM 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.
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.
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Battery Charger Board: Dell Latitude C840 Service Manual
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.
Back to Contents Page
file:///F|/Service%20Manuals/Dell/Latitude/c840/battch.htm (2 of 2) [2/28/2004 8:03:46 AM]
LED Board: Dell Latitude C840 Service Manual
Back to Contents Page
LED Board
DellTM LatitudeTM 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.
1 M2 x 4-mm screws (2)
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LED Board: Dell Latitude C840 Service Manual
Removing the LED Board
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the hinge cover.
3. Remove the two M2 x 4-mm screws.
4. Lift the LED board away from its connector.
Replacing the LED Board
1. Align the two screw holes with the two mounting holes on the bottom case, and
press the board into its connector.
2. Replace the two M2 x 4-mm screws.
Back to Contents Page
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Fan: Dell Latitude C840 Service Manual
Back to Contents Page
Fan
DellTM LatitudeTM 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.
1 fan cables
2 M2 x 4-mm screws (3)
Removing the Fan
1. Follow the instructions in "Preparing to Work Inside the Computer."
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Fan: Dell Latitude C840 Service Manual
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.
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.
Back to Contents Page
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RJ-11/RJ-45 Module: Dell Latitude C840 Service Manual
Back to Contents Page
RJ-11/RJ-45 Module
DellTM LatitudeTM 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.
1 network cable
2 bottom case
3 RJ-11/RJ-45 module
4 modem cable
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RJ-11/RJ-45 Module: Dell Latitude C840 Service Manual
Removing the RJ-11/RJ-45 Module
1. Follow the instructions in "Preparing to Work Inside the Computer."
2. Remove the system board.
3. From outside the bottom case, push in and up on the RJ-11/RJ-45 module while
pulling the side of the bottom case slightly outward. When the module
disengages, lift it out.
Replacing the RJ-11/RJ-45 Module
When replacing the RJ-11/RJ-45 module, hold both cables safely out of the way and
snap the housing down into place. Then route the modem cable through the vertical
slot, through the appropriate posts, and out through the corner of the memory
module/modem cutout.
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RJ-11/RJ-45 Module: Dell Latitude C840 Service Manual
1 vertical slot
2 modem cable
When replacing the system board, ensure that the network cable is safely above the
board and out of the way.
Back to Contents Page
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
Back to Contents Page
Pin Assignments for I/O Connectors
DellTM LatitudeTM C840 Service Manual
USB Connector
Pin Signal
1 VCC
2 -Data
3 +Data
4 Ground
Serial Connector
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
Pin Signal Pin Signal
1 DCD 6 DSR
2 RXDA 7 RTS
3 TXDA 8 CTS
4 DTR 9 RI
5 GND
Parallel Connector
Pin Signal Pin Signal
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
1 STRB# 11 BUSY
2 PD0 12 PE
3 PD1 13 SLCT
4 PD2 14 AFDF#
5 PD3 15 ERROR#
6 PD4 16 INIT#
7 PD5F 17 SLCT_IN
8 PD6F 18-23 GND
9 PD7F 24 DFDD/LPT#
10 ACK# 25 GND
Video Connector
Pin Signal Pin Signal
1 RED 9 CRT_VCC
2 GREEN 10 GND
3 BLUE 11 MSEN#
4 NC 12 DAT_DDC2
5 GND 13 HSYNC
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
6 GND 14 VSYNC
7 GND 15 CLK_DDC2
8 GND
PS/2 Connector
Pin Signal
1 DAT_KBD
2 DAT_SM1
3 GND
4 PS2VCC
5 CLK_KBD
6 CLK_SM1
S-Video TV-Out Connector
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
S-Video
Pin Signal
1 GND
2 GND
3 DLUMA-L
4 DCRMA-L
Composite Video
Pin Signal
5 SPDIF
6 DCMPS-L
7 SPGND
Docking Connector
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
Pin Signal Pin Signal
1 STRB#/5V 101 VGA_GRN
2 PD0 102 GND
3 PD1 103 VGA_RED
4 PD2 104 GND
5 PD3 105 VGA_BLU
6 PD4 106 DOCK_SD/MODE
7 PD5 107 D_IRTX
8 PD6 108 D_IRRX
9 PD7 109 GND
10 GND 110 SPIRQB#
11 DOCK_SPKR 111 SPIRQC#
12 DOCK_MIC 112 DAT_DDC2
13 DOCK_LINE 113 CLK_DDC2
14 DOCK_CDROM 114 SPAR
15 GND 115 SPME#
16 M_SEN# 116 GND
17 POWER_SW# 117 SSERR#
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
18 QPCIEN# 118 SPERR#
19 S1.6M_EN# 119 SLOCK#
20 DFDD/LPT# 120 SSTOP#
21 GND 121 GND
22 NC 122 SDEVSEL#
23 NC 123 STRDY#
24 D_ATCTLED 124 SIRDY#
25 D_PWRLED 125 SFRAME#
26 DOCK_PWR_SRC 126 SCLKRUN#
27 DOCK_PWR_SRC 127 GND
28 DOCK_PWR_SRC 128 SGNTA#
29 GND 129 SREQA#
30 +5VDOCK 130 SGNT0#
31 +5VDOCK 131 SREQ0#
32 +5VDOCK 132 SPCIRST#
33 +5VDOCK 133 SH1SEL#
34 +5VDOCK 134 GND
35 GND 135 SWRPRT#
36 DOCK_PWR_SRC 136 SDSKCHG#/DRQ
37 DOCK_PWR_SRC 137 SDIR#
38 DOCK_PWR_SRC 138 STRK0#
39 DOCK_PWR_SRC 139 SSTEP#
40 GND 140 SDRV1#
41 DOCK_+DC_IN 141 GND
42 DOCK_+DC_IN 142 SMRT1#
43 DOCK_+DC_IN 143 SWRDATA#
44 DOCK_+DC_IN 144 SWGATE#
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
45 DOCK_+DC_IN 145 SRDATA#
46 DOCK_+DC_IN 146 SINDEX#
47 DOCK_+DC_IN 147 GND
48 DOCK_+DC_IN 148 NC
49 GND 149 +5VALW
50 LOW_PWR 150 NC
51 HSYNC 151 GND
52 VSYNC 152 CLK_SPCI
53 GND 153 GND
54 DOCKED 154 SAD0
55 USB_VD1+ 155 SAD1
56 USB_VD1- 156 SAD2
57 GND 157 SAD3
58 USB_VD2+ 158 SAD4
59 USB_VD2- 159 SAD5
60 DOCKOCI# 160 SAD6
61 RUN_ON# 161 GND
62 GND 162 SAD7
63 NC 163 SAD8
64 DOCK_SCLK 164 SC/BE0#
65 DOCK_LRCK 165 SAD9
66 DOCK_MCLK 166 SAD10
67 GND 167 SAD11
68 +12V 168 SAD12
69 AFD# 169 GND
70 ERROR# 170 SAD13
71 ACK# 171 SAD14
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
72 GND 172 SAD15
73 INIT# 173 SAD16
74 SLCT_IN# 174 SC/BE1#
75 BUSY 175 CD/BE2#
76 PE 176 GND
77 SLCT 177 SAD17
78 GND 178 SAD18
79 DAT_SMB 179 SAD19
80 DCLK_SMB 180 SAD20
81 SMB_INIT# 181 SAD21
82 GND 182 GND
83 DAT_DOCKSM1 183 SAD22
84 CLK_DOCKSM1 184 SAD23
85 DAT_DOCKKBD 185 SAD24
86 CLK_DOCKKBD 186 SC/BE3#
87 GND 187 SAD25
88 RI0 188 GND
89 CTS0 189 SAD26
90 RTS0 190 SAD27
91 DSR0 191 SAD28
92 GND 192 SAD29
93 DTR0 193 SAD30
94 TXD0# 194 SAD31
95 RXD0# 195 GND
96 DCD0 196 NC
97 NC 197 NC
98 +5VSUS 198 NC
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Pin Assignments for I/O Connectors: Dell Latitude C840 Service Manual
99 NC 199 NC
100 NC 200 GND
IEEE 1394 Connector
Pin Signal
1 TPB-
2 TPB+
3 TPA-
4 TPA+
Back to Contents Page
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