Brother TD-4000 Service Manual page 45

<For 100/120V model>
(9) Turn the machine upside down. Release the harness of the sub ASSY SW from
the three ribs of the machine. Push the hook of the connector of the sub ASSY
SW and remove it from the connector of the power supply ASSY.
(10) Release the two hooks to remove the sub ASSY SW from the machine.
NOTE: The sub ASSY SW cannot be removed from the machine in this status.
Ribs
Figure 3.4-23 Removing the Sub ASSY SW (For 100/120V model) (1)
Connector (power supply ASSY)
Rib
III - 20
Connector (sub ASSY SW)
Sub ASSY SW
Hook