Dell Precision WorkStation 420 Service Manual page 49

To remove the system board, perform the following steps.
CAUTION: Before you remove the computer cover, see
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
1. Remove the computer cover.
2. Disconnect all cables from their connectors at the back of the computer.
3. Rotate the system power
4. Disconnect all cables from the system board.
5. Remove the RIMMs.
6. Remove the airflow shroud, the primary processor, and the secondary processor or terminal
7. Remove the AGP card brace
8. Slide all externally accessible drives and brackets partially out of the chassis.
9. Slide the hard-disk drive bracket partially out of the
10. Remove the microprocessor cooling
11. Remove the screw that secures the system board to the bottom of the chassis.
12. Slide the system board toward the front of the chassis until it stops.
13. Carefully raise the front of the system board and lift the board out of the chassis at an angle.
To replace the system board, perform the following steps:
1. Carefully replace the system board in the chassis by performing steps 11 through 13 of the removal process in reverse.
2. Push down near each slot to engage the grounding clip onto its corresponding tab.
3. Push evenly on both sides of the system board as you slide and lock it into position (do not twist the system board).
4. Reinstall the mounting screw.
5. Reinstall all components on the system board by performing steps 4 through 10 of the removal process in reverse.
6. Set the jumpers on the new system board so that they are identical to those on the old board, unless you are installing a microprocessor
upgrade.
7. Replace the computer cover, connect cables, and turn on the power. Run the System Setup program to ensure that your settings are correct
and all system board components are correctly reported.
8. Run the Dell Diagnostics.
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supply.
and the AGP video card.
chassis.
fan.
1 System board
2 Screw
"Precautionary Measures."
Figure 28.
card.