Patrick S.Pielin;39;of 121 Kolar Ave.;Liberty Borough;McKeesport;died Saturday;Dec.28;1991;in Presbyterian University Hospital;Pittsburgh.  Born June 15;1952;in Pittsburgh;he was the son of Victor and Sophie Pielin of Mt.Washington;Pittsburgh;who survive.  Mr.Pielin was a graduate of St.Mary of the Mount High School and attended Point Park College.  He had been employed as an electrical designer.  He was a member of St.Eugene Roman Catholic Church;Liberty Borough;and the Musicians’ Union;Connellsville.  In addition to his parents;he is survived by his wife;Jonni Kay Wilkinson Pielin;three daughters;Kelly;Erin and Aimee;all at home;a brother;Vincent Pielin of Pittsburgh;five sisters;Mary Frazer of Pleasant Hills;Carrie Calaffey of Houston;Texas;and Marsha Zinnikas;Christine Tuttle and Vicki Pielin;all of Pittsburgh and his paternal grandmother;Jewel Fitzgerald of Los Angeles;Calif.  Friends will be received Monday from 2 to 4 and 7 to 9 p.m.in the James C.Stump Funeral Home;Sweeney Plan;Rostraver Township;where a Blessing service will be held Tuesday at 10 a.m.;followed by Mass of Christian Burial at 10:30 a.m.in St.Anne Roman Catholic Church;Rostraver Township.  Interment will follow in Belle Vernon Cemetery.  Arrangements are being handled by the James C.Stump Funeral Home Inc.