Dell Precision WorkStation 420 User manual

DellPrecision™WorkStation420SystemsServiceManual
Desktop Chassis —Removing and Replacing Parts
Mini Tower Chassis —Removing and Replacing Parts
NOTE: You can obtain the latest version of this document from the Support section of the Dell Web site at http://www.dell.com.
Notes, Notices, and Cautions
Throughout this guide, blocks of text may be accompanied by an icon and printed in bold type or in italic type. These blocks are notes, notices,
and cautions, and they are used as follows:
Information in this document is subject to change without notice.
©1999 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, Dell Precision, and the DELL logo are trademarks of Dell Computer 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.
Initial release: 30 Nov 1999
NOTE: A NOTE indicates important information that helps you make better use of your system.
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 potentially hazardous situation which, if not avoided, may result in minor or moderate
injury.

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Desktop Chassis —RemovingandReplacingParts:DellPrecision™WorkStation420
Systems Service Manual
Overview
This section provides procedures for removing and replacing the components, assemblies, and subassemblies in the Dell Precision WorkStation
420 desktop chassis system.
Unless otherwise noted, each procedure assumes that the following conditions exist:
lYou have performed the steps in "Precautionary Measures."
lYou have removed the computer cover.
lYou can replace or reinstall a part by performing the removal procedure in reverse order unless additional information is provided.
Recommended Tools
Most of the procedures in this file require the use of one or more of the following tools:
l#2 Phillips-head screwdriver
lA wrist grounding strap as explained in "Precautionary Measures."
Precautionary Measures
Before you perform any procedure in this section, take a few moments to read the following caution for your personal safety and to prevent
damage to the system from electrostatic discharge (ESD).
Overview
Control Panel
Recommended Tools
Chassis Intrusion Switch
Precautionary Measures
Drives
Restarting the System
Power Supply
Computer Cover
System Board Components
Interior Service Label
RIMMs
Internal View
Microprocessor/Heat Sink Assembly
Front-Panel Inserts
Cooling Fan
Expansion Cards
Battery
Expansion-Card Guide
System Board
CAUTION: FOR YOUR PERSONAL SAFETY AND PROTECTION OF THE EQUIPMENT
Before you start to work on the system, perform the following steps in the sequence listed:
1. Turn off the computer and all peripherals.
2. Disconnect the computer and peripherals from their AC power sources. Also, disconnect any telephone or telecommunication lines
from the computer. Doing so reduces the potential for personal injury or shock.
3. If you are disconnecting a peripheral from the computer or are removing a component from the system board, wait 10 to 20 seconds
after disconnecting the computer from AC power before disconnecting the peripheral or removing the component to avoid possible
damage to the system board.
4. Wear a wrist grounding strap, and clip it to an unpainted metal surface, such as the padlock loop on the back of the chassis. If a wrist
grounding strap is not available, touch any unpainted metal surface on the back of the computer or on the computer chassis, such as

Restarting the System
To restart the system and reset the chassis intrusion detector, perform the following steps:
1. Replace the computer cover and reconnect the computer and peripherals to their power sources and turn them on.
ALERT! Cover was previously removed.
2. To reset the chassis intrusion detector, enter System Setup, select System Security,andresetChassis Intrusion to Enabled or
Enabled-Silent.
Computer Cover
Figure 1. Computer Cover Removal
To remove the desktop chassis computer cover, perform the following steps:
1. Turn off your computer and peripherals, and observe the Caution for Your Personal Safety and Protection of the Equipment described in
"Precautionary Measures."
2. If you have installed a padlock through the padlock ring on the back panel, remove the padlock.
3. Press in on the two securing buttons until the cover is free to swing up (see Figure 1).
4. Raise the back of the cover, and pivot it toward the front of the computer.
5. Lift the cover off the hooks at the front of the chassis.
Figure 2. Computer Cover Replacement
thepowersupply,todischargeanystaticchargefromyourbodybeforetouchinganythinginsidethecomputer.Whileyouwork,
periodically touch an unpainted metal surface on the computer chassis to dissipate any static electricity that might harm internal
components. Also avoid touching components or contacts on a card and avoid touching pins on a chip.
5. Verify that the standby power light-emitting diode (LED) on the system board is not on. If it is on, you may need to wait 10 to 30
seconds for it to go out (see Figure 22 or the internal service label).
NOTE: When you start the system, the chassis intrusion detector will cause the following message to be displayed at the next
system start-up:
NOTE: If a setup password has been assigned by someone else, contact the network administrator for information on resetting the
chassis intrusion detector.
1
Securing buttons (2)

To replace the computer cover, perform the following steps:
1. Check all cable connections, especially those that might have come loose during your work. Fold cables out of the way so that they do not
catch on the computer cover. Make sure cables are not routed over the drive bracket—they will prevent the cover from closing properly.
2. Check to see that no tools or extra parts (including screws) are left inside the computer's chassis.
3. Facing the left side of the computer, hold the cover at a slight angle as shown in Figure 2.
4. Fit the three cover hooks into the rectangular slots on the chassis. (It might be helpful to look down into the chassis to verify that the hooks are
in place.)
5. Pivot the cover down toward the back and into position. Make sure that the two securing buttons click into place.
Interior Service Label
Figure 3 shows the location of the interior service label on the inside of the top cover. This label shows the location of components within the
chassis and locations of system board components and connectors. It also contains an important notice that provides instructions you need to
follow to help prevent damage to your system board while you troubleshoot and service the computer system.
Figure 3. Interior Service Label
Internal View
Figure 4 shows the chassis with the top cover removed.
Figure 4. Chassis Orientation View
1
Securing buttons (2)

Front-Panel Inserts
Figure5.5.25-Inch Front-Panel Insert Removal
To remove a 5.25-inch front-panel insert, perform the following steps:
1. Hold the inverted top cover with the front facing you.
2. From the front of the top cover, use your thumbs to press inward on the insert until it snaps free of the cover.
To replace a 5.25-inch front-panel insert, position the two ring tabs over the posts on the inside of the bay opening, and then press the ring tabs
over the posts.
Expansion Cards
The Dell Precision 420 systems provide five 32-bit Peripheral Component Interconnect (PCI) expansion card slots. Slot 5 is shared with the RAID
port function.
The system contains five 32-bit expansion slots and a 32-bit AGP Pro 50 (4X) slot. If you use an AGP Pro 50 card, it occupies the AGP slot and
may occupy PCI slots 1 and 2. (See Figure6 for examples of these cards.)
Figure 6. Expansion Cards
1
Externally accessible drive bays
2
Hard-disk drive bracket
3
System board
4
Expansion card slots
5
Padlock ring
6
I/O panel connectors
7
Security cable slot
8
AC power receptacle
9
Power supply
10
Drive data cable
1
Front-panel insert
2
Ring tabs (2)
3
Posts (2)
NOTE: Before disconnecting a peripheral from the system or removing a component from the system board, verify that the standby
power LED on the system board has turned off. For the location of this LED, see Figure 22.

Figure 7. AGP Pro50 Card Extension
Figure 7 shows the card extension that may occupy PCI slots 1 and 2.
The following is a list of valid expansion-card combinations:
lOne AGP card and five PCI cards
lOne AGP card, four PCI cards, and one RAID card
lOne AGP Pro50 card and four PCI cards
lOne AGP Pro50 card, three PCI cards, and one RAID card
Expansion Card Removal
To remove an expansion card, perform the following steps.
1. Remove the computer cover.
2. Disconnect any cables connected to the card.
3. Unscrew the mounting bracket of the card you want to remove.
4. Grasp the card by its outside corners, and ease it out of its connector.
5. If you are removing the card permanently, install a metal filler bracket over the empty card-slot opening.
6. Replace the computer cover, and reconnect your computer and peripherals to their power sources and turn them on.
ALERT! Cover was previously removed.
7. To reset the chassis intrusion detector, enter System Setup, select System Security, and reset Chassis Intrusion to Enabled or
Enabled-Silent.
1
32-bit PCI expansion card
2
32-bit AGP card
CAUTION: Before you remove the computer cover, see "Precautionary Measures."
NOTE: Installing filler brackets over empty card-slot openings is necessary to maintain Federal Communications Commission
(FCC) certification of the system. The brackets also keep dust and dirt out of your computer.
NOTE: After you remove and replace the cover, the chassis intrusion detector will cause the following message to be displayed at
the next system start-up:

Expansion-Card Guide
Figure 8. Expansion-Card Guide Removal
To remove the expansion-card guide, perform the following steps:
1. Remove the hard-disk drive bracket.
2. Face the computer from the front.
From the outside of the chassis, press in with your fingers on the two tabs on the left side of the expansion-card guide (see Figure8). This
will release the left tabs of the card guide from the chassis.
3. Rotate the released side of the card guide away from the chassis.
The left side of the card guide will swing away from the chassis. With the left side of the card guide away from the chassis, you can then pull
the card guide back and out of the chassis, which releases the two right tabs.
Control Panel
Figure 9. Control Panel Removal
To remove the control panel, perform the following steps:
NOTE: If a setup password has been assigned by someone else, contact your network administrator for information on resetting
the chassis intrusion detector.
1
Left tabs (2)
2
Right tabs (2)
1
Thermal sensor cable
2
Control panel cable
3
Screw
4
Speaker cable
5
Chassis intrusion switch
cable
6
Control panel
7
Alignment hole
8
Guide pin
CAUTION: Before you remove the computer cover, see "Precautionary Measures"

1. Disconnect the control panel cable from the PANEL connector on the system board (see Figure 22 for the location of the PANEL connector).
2. Remove the mounting screw that secures the control panel to the chassis.
3. Disconnect the chassis intrusion switch cable connector from the control panel.
4. Disconnect the thermal sensor cable connector from the control panel.
5. Disconnect the speaker cable connector from the control panel.
6. Remove the control panel and cable from the chassis.
To reinstall the control panel, perform the removal procedure in reverse.
When you reinstall the control panel, be sure to align the control panel alignment hole and the guide pin located on the left side of the chassis front.
Chassis Intrusion Switch
Figure 10. Chassis Intrusion Switch Removal
To remove the chassis intrusion switch, perform the following steps:
1. From inside the chassis, slide the chassis intrusion switch to the side to release it from the chassis.
2. Disconnect the chassis intrusion switch cable connector from the control panel (see Figure9).
3. Remove the chassis intrusion switch and cable from the chassis.
Note the routing of the chassis intrusion cable to ensure the replacement is routed in the same manner.
4. Install the replacement chassis intrusion switch.
5. Replace the computer cover. Then reconnect your computer and peripherals to their power sources, and turn them on.
6. To reset the chassis intrusion detector, enter System Setup, select System Security,andresetChassis Intrusion to Enabled or
Enabled-Silent.
Drives
1
Control panel
2
Screw
3
Chassis intrusion switch
CAUTION: Before you remove the computer cover, see "Precautionary Measures"
NOTE: After you remove and replace the cover, the chassis intrusion detector will cause the following message to be
displayed at the next system start-up:
ALERT! Cover was previously removed.

Figure 11. Drive Locations
Diskette Drive Removal
To remove the 3.5-inch diskette drive assembly, perform the following steps:
1. Rotate the system power supply up and out of the system (see Figure 20).
2. Disconnect the DC power cable from the back of the diskette drive.
3. Disconnect the interface ribbon cable from the back of the diskette drive.
The other end of this ribbon cable is connected to the DISKETTE connector on the system board (see Figure 22 for the location of the
DISKETTE connector).
Note the routing of the DC power and interface ribbon cables through the chassis as you disconnect them. It is important to route the cables
properly when you replace them to prevent them from being pinched or crimped.
4. Press down on the retaining-tab release button (see Figure 12) and pull the drive assembly forward to remove it from the chassis.
Figure 12. Diskette Drive Removal
5. Remove the screw securing the diskette drive to the bracket (see Figure 13).
Figure 13. 3.5-Inch Drive Bracket
NOTE: In all of the following procedures, left and right refer to your left and right as you face the front of the computer.
1
Hard-disk drives
2
5.25-inchdrives
(CD-ROM drive
shown)
3
3.5-inch diskette
drive
CAUTION: Before you remove the computer cover, see "Precautionary Measures"
1
Retaining-tab release button

6. Rotate the left side of the diskette drive up until the drive is clear of the retaining tabs.
When you replace the 3.5-inch diskette drive on the bracket, be sure that the two retaining tabs on the right side of the bracket engage the
mounting holes in the side of the 3.5-inch diskette drive. Then replace the screw that holds the diskette drive to the bracket. To replace the 3.5-inch
diskette drive/bracket assembly in the chassis, slide the bracket tabs into the guides on the chassis until the bracket snaps into place. Reconnect
the DC power and interface cables.
5.25-Inch Diskette, LS-120 SuperDisk, Tape, or CD-ROM Drive Removal
To remove a diskette, LS-120 SuperDisk, tape, or CD-ROM drive, perform the following steps:
1. Remove the computer cover.
2. Disconnect the DC power cable and data cable from the back of the drive.
3. Squeeze the metal tabs that extend from each side of the drive bracket toward each other.
4. Pull the bracket out of the bay (see Figure 14).
Figure 14. 5.25-Inch Drive Removal
5. Turn the drive/bracket assembly upside down and remove the four screws that secure the drive to the bracket (see Figure 15).
Figure 15. 5.25-Inch Drive Bracket
1
3.5-inch diskette drive
2
Retaining tabs (2)
3
Bracket
4
Screw
1
Bracket tabs (2)
NOTE: For easier access inside the chassis, you may want to rotate the power supply out of the way temporarily. To do so, see Figure
20.