A well-known Wilmington doctor charged with illegal use of prescription drugs was placed on probation yesterday by a district court judge. Dr. Hubert Eaton, Jr. Pleaded guilty to two misdemeanor charges of obtaining a controlled substance through the use of an illegal prescription. He received a 90- day suspended jail sentence, a 500-dollar fine and was placed on two years probation. Eaton's medical license has also been suspended until a November hearing before the state medical board.