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3. Remove the PCB cover and set aside. 106 54-0147 Replacing the Main PCB Replacing the Main PCB . With a PC connected to the ADCU’s maintenance port, apply power to the antenna unit. 2. Record the system serial number for later re-entry (the serial number is listed at the beginning of the startup sequence, as shown in Appendix F on page 143). 3. Disconnect power from the antenna unit and the IRD. 4. Remove the PCB cover, as explained in “Removing the Main PCB Cover” on page 106. 5. Disconnect a