peugeot speedfight 100?

Hi i have a peugeot speedfight 100 that has just recently broke down on me i took it to a mechanic and he said it was the cdi system , this was changed but it is still the same it has been looked at very well such as the carb has been cleaned and all alround the bike has been taken apart but the problem is still there and dont have a spark, replacement cdi has been put in but has now popped and faulty. has anybody any ideas as cdi's are £100 a time cant afford to keep changing them.