HP DC7800 - Manual (Page 200)

12. Lift the rear of the system board until it clears the chassis (3), and then remove the system board
from the chassis (4).
To install the system board, reverse the removal procedure.
NOTE: When replacing the system board, you must also change the chassis serial number in the
BIOS.
Rear Chassis Fan
1. Prepare the computer for disassembly ( Preparation for Disassembly on page 159 ).
2. Remove the computer access panel ( Computer Access Panel on page 163 ).
3. Remove the optical drive ( Removing the Optical Drive on page 170 ).
4. Remove the hard drive ( Hard Drive on page 174 ).
5. Remove the hard drive cage ( Hard Drive Cage on page 178 ).
6. Remove the heatsink ( Heatsink on page 184 ).
7. Disconnect the fan cable from the system board.
8. Remove the system board ( System Board on page 187 ).
9. Remove the four screws that secure the fan to the chassis (1).
188 Chapter 9 Removal and Replacement Procedures Ultra-Slim Desktop (USDT) Chassis