Well the ones I ordered from tower are the ones stated above and they work in my tanks.I'm pretty sure all the S&S tanks use fm crystals,But I could be wrong.The symptoms you described are usually the crystals,when one or the other of the set goes out (the transmitter and receiver can not comunicate with each other.If the board goes(it usually is just some features that quit working,allthough sometimes it will smoke and self destruct the board itself).There is most likely nothing wrong with the boards at this point.I have had several tanks do the same thing your's is doing and it was just a bad crystal. BIGMIG

P.S. I'm pretty certin the S&S radio's are FM because I don't think you could get AM radio to work with FM crystals or visa-versa.