I had a very peculiar thing happen this afternoon. I was aetting up for a client. I work at an office with a dental chair like set up. I covered my cord, plugged into the EMS300, slung my cord with sleeve across the surgical table and BAM! I apparently hit a anrea on the chair that was "live" -- apparently there was some sort of electrical short in the chair. Needless to say the connection caused a significant spark, leaving behind a significant hole in the metal "male" end of the power chord. I went to Radio Shack as suggested and bought the part #/catalog #42-2433 6Ft. Audio Cable (one end 1/8 inch and one end 1/4 inch). Both my machine and power source Eikon EMS300 are working. But, I am not sure if my power source is behaving properly. With no needle & no tube set up, running it at 9.0v, 86-87CPS, Duty is switching between 27% and 28% -- should I be concerned? It is my understanding that duty should be between 40-50% with a needle. So, then I put in a 1214RS (Mithra) & Disposable tube;(RDTRL-A(14) and ran at 9v, saw 80-82 CPS, but the duty was running at 79-80%. Is this right? I believe the duty should be between 40-50% with the the previous mentioned needle and tube, correct?