In Commonwealth v. Bischof, 420 Pa. Super. 115, 616 A.2d 6 (Pa.Super. 1992), following a negotiated plea of guilty to two burglaries, the appellant was sentenced to two concurrent terms of time served to 23 months imprisonment. He was subsequently paroled and later committed a parole violation. At the parole violation hearing, the court directed that the appellant serve the back time for each sentence consecutively, despite the fact that the two sentences were initially imposed concurrently as part of a negotiated plea agreement. The Court reversed on appeal. The Court noted that, generally, the courts have jurisdiction to modify sentences only in the first 30 days after imposition and that to change sentences that were originally made to run concurrently to consecutive sentences more than thirty days after imposition, is an illegal modification of sentence which constitutes further or double jeopardy. 616 A.2d at 10.