PHL CTLR EXPERIENCED OPERROR AT 6000 FT WHEN MISJUDGING TIME AND DISTANCE REQUIRED TO SEPARATE OPPOSITE DIRECTION TFC.

Narrative

I WAS WORKING MODERATE TFC. I TOOK A HDOF ON THE ACFT GOING NBOUND AND WHO WAS TUNNELING BELOW PHL DEPS. THIS IS A SOMEWHAT UNUSUAL POS FOR THIS ACFT. I CLBED THE ACFT TO 10000 FT AS SOON AS POSSIBLE. I HAD TAKEN A HDOF ON THE LJ60; SBOUND (OPPOSITE DIRECTION TO THE ACFT) AT 6000 FT. THIS ACFT WAS DIRECT TO ITS DEST; ALSO A LITTLE OUT OF THE ORDINARY. THE LJ60 ALSO HAD TFC BELOW IT THAT PREVENTED ME FROM DSNDING IT IN A TIMELY MANNER. ALSO AT THAT SAME TIME; I HAD TO INITIATE A MANUAL HDOF TO PTC TRACON ON AN IFR OVERFLT THAT WOULD NOT AUTO-HDOF. ABOUT 6 SECONDS AFTER COMPLETING THIS HDOF; THE CONFLICT ALERT WENT OFF AND SEPARATION WAS LOST. I ISSUED AN IMMEDIATE TURN TO THE LJ60 AND BOTH ACFT WERE RESPONDING TO TCAS ALERTS. THE UNUSUAL POS OF THE ACFT AS THEY WERE HANDED OFF TO ME WERE A FACTOR. BUT THE MANUAL HDOF OF THE OVERFLT WAS ALSO A MAJOR FACTOR. HAVING BOTH ACFT ON MORE STANDARD RTES (AWAY FROM PHL DEPS) AND BEING ABLE TO HDOF THE OVERFLT THROUGH AUTOMATION WOULD HAVE PREVENTED THIS INCIDENT.