3DR Quadcopter single motor power loss

Help
10

Hi

Connections on my Quad:

  1. Main power line (6 wires) from the 3DR Power monitor (BEC?) to the “Power” socket on the Pixhawk
  2. “Futaba” type connector (4 wires) from 3DR PDB to Pixhawk

The two-wire connector (“Futaba” ) type isn’t connected .
Where should I connect this, as it’s described as “Backup power” (or somesuch) in the manuals?

If this is the grounding between the Pixhawk & the PDB\ESCs then that might well be the problem!

If you can let me know how to connect this, I’ll try this evening after work.

Thanks