A Waltham man was sentenced to 18 months in federal prison after he was convicted of using insider information on a Devens-based power-technology company to provide profitable tips to his golfing buddies, including Lowell attorney and city golf champ Douglas Parigian. Eric McPhail, 41, of Waltham, was sentenced on Monday by U.S. District Court Judge Denise J. Casper to 18 months in prison followed by two years of supervised release, according to the U.S. Attorney's Office.