Well if you have a nice brite light on the transmitter and the lights are flashing on the tank you know you are getting power two both of them.Like I said before if the transmitter and receiver are not comunicating with each other,thats as far as you are going to get.There could be other problems,but untill you rule out bad crystals you will be wasting your time and just guessing.When the lights just flash on the tank,it is not getting the signal to turn everything on.Until this happens it is just going to set there flashing- I have had this same thing happen to me with several tanks.......New ones right out of the box.

BIGMIG

P.S. General rule of thumb if you try to use a battery of lower voltage than required to operate your tank it most likely will not hurt anything,but using a battery of more voltage than it was made for can do dammage to it.