Helionetics Inc., a diversified high-technology company, in Irvine reported a second-quarter profit of $617,000, or 2 cents a share. That compares with $478,000, or 4 cents a share, for 1993’s second quarter, which included a loss of $9,000 from discontinued operations. Revenue rose to $18.9 million from $4.3 million. Year-to-date profit totaled $1.5 million, or 6 cents a share, down from $1.6 million, or 13 cents a share, recorded for the first half last year. Revenue increased to $35.2 million from $7.8 million.