My partner runs the f75 and I run the T2 (almost the same thing), we both have experienced the same problem over the years. When we sent our machines to 1st Texas Felix (the guy who did the repairs) said he "shielded" the coil. Both our machines worked perfectly after that. It seems as though you need the same thing. It is a real drag when it happens because no target sounds good. I hope you get it ironed out.