Pirates: Manager Chuck Tanner had two reasons to smile last night. First, his last-place Pirates did not lose. Second, since their game with the St. Louis Cardinals at Three Rivers Stadium was rained out, Tanner had the opportunity to watch his son pitch in his major league debut. Bruce Tanner, 23, a right-handed pitcher for the Chicago White Sox, was scheduled to start against the Seattle Mariners. "My brother has a satellite dish, and I'm going up to his house to watch the game," Tanner said. "I don't know how many people are going to be there but I can guarantee two things: I'll have the best front-row seat, and there won't be any talking allowed in the room. " Tanner had insurance in case of any technical difficulties with his brother's video system. Pirate third baseman Bilt Madlock, another satellite-dish owner, promised to videotape the game for his manager. "I've never really had much of a chance to see Bruce pitch," Tanner said. "I've always been working. I'm looking forward to this." Bruce Tanner was Chicago's fourth selection In the June 1983 free agent draft. After a 12-4 season at Class A Appleton in 1984, he was promoted to Class AAA Buffalo this season. The White Sox called him up earlier this week . . . Reliever Don Robinson, who strained a ligament in his right knee while warming up in Chicago Sunday, won't be available to pitch tonight. He was given an Injection in the knee Tuesday and should be able to pitch in a few days, Tanner said . . ..Madlock, the Pirates' captain, said the team will take a strike authorization vote by secret ballot in Montreal Monday night before the Pirates play the Expos.