Hi, All, I appreciate for you all to response to my inquiry published on the list. It made me know the difficulty existing in the way of using flyback coil and learned more knowledge on the Tesla. In fact , the subject is very strange for me. However, I try to make a ferrite coil to produce HV with more power than TV coil. If has some progress, I'll publish it. -- Sincerely Yours, Attn: Zhao