Ok so I have had my solar d770 servo in my buggy for almost a year now and it's worked great. I decided to wire up 7.4 volts to the reciever and pulled the red wire from the esc. Now at full trottle the servo jumps far left and comes back to center. When powered from the bec it's fine. Plugged in a protek servo rated for 7.4 as well and did the same thing. What did I do wrong. Do I need to pull the black wire for the esc? Do I need to pull the black wire from the battery. My only thought is that you can't have two negatives for reference?

Again soldered 7.4 from the esc battery terminals to a lead to power the esc (receiver rated at 7.4). Then pulled the red wire from the esc lead. Everything pugged in as normal at the reciever.

I know I could wire 7.4 to the servo direct but this is all soldered up nice and wondering why this isn't working.