Tri-Star Pictures reported that Columbia Pictures, a unit of Coca-Cola, has completed the acquisition of half of Home Box Office's stake in Tri Star . . . Wickes Cos. said that its offer to exchange seven of its common shares for each of its $250 preferred stock has expired and that 2.8 million shares of the preferred had been tendered at the close of business Monday . . . Chatsworth-based Powertec filed a countersuit against Scivest and its chairman, Paul J. LaBrie, claiming that the New Hampshire firm overstated its assets by $1.4 million when Powertec agreed to buy it in November.