Service Manual

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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. 

Summary of content (44 pages)

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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 Batter
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Back to Contents Page Battery Charger Board 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. 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.
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Back to Contents Page Battery and Module Bay Latches 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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Back to Contents Page
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Back to Contents Page 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.
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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.
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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.
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Back to Contents Page Microprocessor Module 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. 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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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.
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Back to Contents Page Display Dell™ Latitude™ 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. 1 display 2 hinge cover 3 M2.
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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 4. Open the display and lift off the hinge cover. key and the hinge cover until the hinge cover pops off. Display Assembly 1 M2.5 x 6-mm screws (2) 1. Remove the hinge cover.
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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.
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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 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.
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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.
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Back to Contents Page Fan 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. 1 fan cables 2 M2 x 4-mm screws (3) Removing the Fan 1. Follow the instructions in "Preparing to Work Inside the Computer." 2. Remove the system board. 3.
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Back to Contents Page 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.
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1 captive screw 2 pull tab 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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Back to Contents Page 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. 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.
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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. 1 keyboard cable 2 keyboard interface connector 3 system board 7. Disconnect the keyboard cable and lay the keyboard aside. Replacing the Keyboard 1.
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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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Back to Contents Page LED Board 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. 1 M2 x 4-mm screws (2) 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.
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Back to Contents Page Palm Rest 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. 1 pull loop NOTICE: The reserve battery provides power to the computer's time RTC and NVRAM when the computer is turned off.
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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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Back to Contents Page Pin Assignments for I/O Connectors Dell™ Latitude™ C840 Service Manual USB Connector Pin Signal 1 VCC 2 -Data 3 +Data 4 Ground Serial Connector 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 1 STRB# 11 BUSY
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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 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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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 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 G
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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
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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 99 NC 199 NC 100 NC 200 GND IEEE 1394 Connector Pin Signal
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Back to Contents Page Reserve Battery 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. 1 palm rest bracket 2 reserve battery 3 reserve battery cable NOTICE: The reserve battery provides power to the computer's RTC and NVRAM when the computer is turned off.
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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.
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Back to Contents Page RJ-11/RJ-45 Module 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. 1 network cable 2 bottom case 3 RJ-11/RJ-45 module 4 modem cable Removing the RJ-11/RJ-45 Module 1. Follow the instructions in "Preparing to Work Inside the Computer." 2.
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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.
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Back to Contents Page System Board 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. 1 M2.5 x 4-mm captivewasher screws (3) 2 system board 3 network connector 4 modem connector 5 network cable cover 6 M2.
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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.
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Back to Contents Page
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Back to Contents Page 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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Back to Contents Page Microprocessor Thermal-Cooling Assembly 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. 1 microprocessor thermalcooling assembly 2 microprocessor retaining clip Removing the Microprocessor Thermal-Cooling Assembly 1.
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1 microprocessor thermalcooling assembly 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.
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Back to Contents Page Dell™ Latitude™ C840 Service Manual Notes, Notices, and Cautions Notes, Notices, and Cautions 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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Back to Contents Page 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 1 M2.5 x 20-mm screw 1.
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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. Replacing the Memory Modules 1. If you only have one memory module, install it in the socket labeled "DIMM A.
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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.
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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.
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Back to Contents Page Video Graphics Board 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. 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. 3.