780 Model Roomba Dis-assembly procedure
The first step in taking apart your 700 model Roomba including the 780 is to remove the Designer ring that surrounds the top control panel. Care must be exercised when removing the ring since the bottom end of the ring near the dust bin has two plastic tabs that hold the bottom in place and can easily be broken off of the ring.
Pry up on both sides of the ring with a thin bladed screwdriver where you see the two yellow arrows. As you pry up keep watch for the front of the ring to clear the front bumper IR sensor (Red arrow)
Once the ring is free of the IR sensor, continue to apply upward pressure to the ring until all portions of the ring are free from the small plastic holders that are spaced around the ring. Then tilt the ring up beginning from the IR sensor towards the dust bin until the ring is free.
Flip the Roomba over and remove the side brush, then loosen the 4 phillips head screws and remove the battery cover and bottom plate. Remove the battery, the side brush module, the two drive wheel modules and the front swivel wheel. Remove the 10 small phillips head screws from the bumper retaining ring and lift off the bumper retainer.
Flip the Roomba over and remove the plastic half ring from the bottom portion of the control panel. This will expose 4 more screws that will need to be removed before the top half of the Roomba can be removed exposing the user control buttons and Printed Circuit Assembly Board.
Now remove all the phillips head screws securing the top plate including 4 more screws that become visible when you lift the front carry handle. Also lift the front bumper up and off of the top assembly
Use a small flat blade screwdriver to pry up the opaque plastic cover surrounding the Clean button.
Once the opaque plate is removed then 4 additional screws will be revealed. Loosen the 4 screws and lift out the display console. Now the top can be lifted away from the bottom by lifting up on the carry handle to expose the Printed Circuit Assembly Board.
There are 5 small phillips head screws that secure the PCAB to the bottom base unit. Once those are removed then to remove the PCAB just disconnect the connectors from both the top and underneath portions of the PCAB,