You question needs clarification and your boyfriend needs a criminal defense attorney to get ou of this mess. If he cannot afford a private lawyer, he should apply for a public defender.
Your boyfriend needs to talk with an experienced criminal defense attorney. If he cannot afford one, I recommend that he make an application with the public defender. Good luck!
My guess is that there is important information missing here necessary to answer your question, but I'll take a stab at it. IF your boyfriend was physically arrested, processed, and taken to jail on the new charges then he is entitled to preliminary arraignment "without unnecessary delay"--if arrested with an arrest warrant, then Rule 516 of the Pennsylvanian Rules of Criminal Procedure controls; if arrested without a warrant then Rule 519 is the guide. "unnecessary delay" is not defined but it is hours not a week. What I suspect happened here is that the new charges were initiated by a criminal complaint filed at a magistrate's office and sent to him with a Criminal Summons that sets a date for the preliminary hearing. Preliminary arraignment occurs in conjunction with the preliminary hearing in cases initiated by Criminal Summons. If the probation officer learned of the Summons procedure, he/she could well have asked the court to issue a detainer. That's why he is in jail without having been preliminarily arraigned. I agree completely with my colleagues, he needs criminal defense counsel now.
I agree with the other counsel; if you want to try to learn the reason why he has not been arraigned or received paperwork you can either call the MDJ's office where the charges were filed or check the MDJ docket on the PA UJS web portal using your boyfriend's name. That will tell you both where the charges were filed and whether a summons was sent. Your boyfriend needs a lawyer for the PV and the new charges; if he can't afford private counsel he should put in a prison request for a public defender immediately. One other bit of advice-if you are speaking to him on the phone do not discuss his new charges or the PV. Calls from Lancaster County prison are routinely monitored and used against individuals at trial or as leverage in plea negotiations. Good luck.