Speedo blown up...

[j pearce]

Synopsis: 1. stick LRP sphere into D4 2. plug it in 3. make sure the switch is OFF 4. unplug the speedo wire from the receiver (in order to move the receiver) 5. Boom, negative speedo - receiver wire burns in a huge ball of smoke…
I don’t understand how it could do anything if it was switched off which it was! Anyway, I haven’t touched it since so I was wondering if it was salvageable as it appears to only be the wire that has melted and no smoke came from the unit itself…
If not then never mind but I was wondering if I should try it with the motor and see what happens, or will that damage everything else?
cheers