Culminating weeks of rumors, KNBC-TV general manager Reed Manville abruptly resigned Friday.NBC O&O president and network daytime head John Rohrbeck, who is taking over the top station job temporarily, has vowed to “reenergize” the station. Insiders said Rohrbeck hopes to have the job filled within two months, when he will return to his corporate base in New York. Rohrbeck ran the station with an iron fist from 1984 until November 1991, when he was promoted to president of the NBC TV stations. His appointment of Manville,who had no previous g.m. experience, as his successor in the nation’s second-largest TV market came as a surprise to competitors. Some suspected that Rohrbeck was trying to run the station long distance from New York, which they considered a virtually impossible feat. At the time of his appointment, Manville was a little-known, 11-year vet of the O&O group who had held a variety of financial administration positions. He was the station’s sales planning manager when he was elevated over a number of other higher-ranking execs to the top spot. Improved ratings cited Rohrbeck issued a statement Friday praising Manville for improving the station’s news ratings and his handling of retransmission consent negotiations with cable operators. But the station was wracked by dissension during his two-years-plus tenure. There were complaints about treatment of employees, minorities, news content and other issues that have generated headlines in recent months. In a 30-minute meeting with news staffers announcing Manville’s departure Friday, Rohrbeck said he would hire a diversity officer to oversee the station’s minority hiring practices. While he emphasized the station’s strong affirmative action record, sources said Rohrbeck indicated that there was room for improvement. Hoffman impact Rohrbeck is also said to be pleased with the direction of the station’s news, which has changed a great deal in the year since news director Mark Hoffman arrived from Chicago. Rohrbeck provided a strong endorsement of Hoffman’s performance and his ability to put fresh material into the entire 2 1/2-hour early evening news. The sources said Rohrbeck believes some newsroom staffers who have griped about the new direction are resistant to change. He has told subordinates that other top managers at the station will stay in their jobs. One network insider called Manville a “scapegoat” and a victim of bad timing. Since his arrival, the L.A. market has been plagued by a weak economy, riots, fires and earthquakes. That, coupled with the restructuring in the TV industry, had created a great deal of tension within the station. In contrast, Rohrbeck had run a smooth ship with very little internal discord and virtually no press leaks. Well-timed exit? Still, one source noted that Rohrbeck left the market at the opportune time. “It would have been tough enough (for Rohrbeck) to get through it,” the network exec suggested. “Here was a new guy, so he was an easy target. Things had gotten to the point … that it would have been too difficult and taken too long to overcome all the problems. It required a change of management.” There has been widespread speculation that Rohrbeck would seek to relocate to the West Coast. But sources suggest that he is intent on staying in New York. While the O&O heads for the other webs work outside of Gotham, Rohrbeck also has the additional responsibilities of overseeing the network’s daytime schedule.