Resdel Industries in Newport Beach said it has sold the telephone repair division of its San/Bar subsidiary for $2.8 million to Clapper & Co., a privately held firm in Fullerton. San Bar's repair business was unprofitable and did not fit well with Resdel's main line of business: the manufacture of electronic communication equipment, according to Resdel spokesman Bruce G. Rossiter. Rossiter said that San/Bar's repair business had fiscal 1987 sales of about $1 million, which was "insignificant" compared to total San/Bar revenues of $12.5 million for fiscal 1987, which ended June 30. San/Bar, a maker of telephone and digital microwave equipment, was bought in September in a stock swap valued at $15 million. Resdel sold the division for $2.8 million in notes, to be paid by Clapper & Co. over five years. The Fullerton company is owned by William J. Clapper, who is also owner of Smith Spece & Co., a Fullerton investment banking firm. Clapper was not available for comment Thursday.