Sam Zell has cut his first check - $250 million towards the purchase of Tribune Co., parent of the LAT. Zell purchased 1.47 million newly issued shares of Tribune at $34 each and a $200 million note that pays interest of 4.81 percent a year, according to a regulatory filing. Zell will be able to participate as a Tribune director (he'll be chairman once the company goes private, presumably by the end of the year). Yesterday came another step when federal antitrust regulators approved the deal. That's separate, however, from action by the Federal Communications Commission. Federal rules prevent ownership of a television station and a newspaper in the same market, so Zell & Co. would need a bunch of FCC waivers. Otherwise, the deal could be toast - and some at Tribune still believe it could happen.