K90 Controller described losing a VFR target; noting similar situations are commonplace and the facility ASR-8 system needs requires attention.

Narrative

I took a hand off from PVD on a VFR aircraft landing 5B6. About 30 seconds after I took the hand off the RADAR system dropped the target which was at 5500 FT. I realized that the aircraft was missing from my RADAR scope and began to try and locate the call sign. The aircraft was not in my Coast/Suspend list. I called over to PVD to see if the aircraft had cancelled because there was another aircraft just entering my airspace on a 1200 at 5;500 FT. PVD said no and was not familiar with the aircraft in question. I did not have a beacon code or call sign. The aircraft finally checked in. I had him IDENT to see if it is the aircraft squawking VFR. There was no IDENT observed and I immediately called the aircraft 'RADAR Contact Lost'. The pilot showed a little concern saying 'what do you want me to do then'. I advised him to maintain VFR to his destination and explained the situation. The aircraft dropped off at FMH 264/028. I finally got him back after about 10 miles of flight. This is an on going issue with this RADAR. We are now getting into the busier traffic and I fear this may result in an aircraft incident. Recommendation; truly fix this RADAR so that it works properly. A huge amount of work has been done to the ASR-8; including a new Beacon System. This has not solved the problem; because everyday a situation like this happens. We mitigate it some by placing the ARTS in a RADAR flash to the maintenance scope; but that is not an efficient way of handling aircraft.