It depends what you do to violate probation. Possession of Controlled Substances in PA is a misdemeanor. If you are charged with robbery while on misdemeanor probation, you'd be violated and would almost certainly go to jail If, however, you where charged with failure to pay fines/costs or a relatively minor offense such as possession of a small amount of marijuana, you probably wouldn't go to jail for a violation. It really depends on the specific facts of your particular situation.