You and me both!!

As a recap of op:
The MGM is giving the error beeps with or without the switch on. What really trips me out is that if I have one of the power leads bullet plugs pulled out of the MGM, it still gives me the beeps!

So like I said midway through this thread, it's pulling it's juice to do that through the receiver.

I think I'm gonna sell this damn thing and give up on running 6s and get a Quark!

OK, that symptom sounds familiar. When I first got my MM ESC, I wanted to test it out and set up some basic programming. So, I put in a receiver pack into the RX and plugged in the MM controller cable without removing the red wire and no main battery pack. As soon as I did this, I heard arming tones from the motor! And, like you, it didn't matter what position the switch was in.

All I did was remove the rx pack and it worked fine. It also worked fine if I used the rx pack but removed the red wire in the throttle cable. This sounds A LOT like what you are seeing, but I didn't blow the ESC or receiver.

What might be happening is the ESC is pulling power to arm the motor through the throttle cable. It would then make sense that this would blow receivers because the PCB traces aren't designed to handle that kind of current.

I'm sorry if I wasn't clear enough before. OI relates to BEC in that OI ESC's do NOT have BEC capability at all if they are truely OI. This is because the main battery is not connected to anything except for the Power Side of the OI ESC. There is no physical connection between the Power Side of the OI ESC and the rest of the system. This is why you need a second battery (reciever pack) to power EVERYTHING including the OI ESC itself.