A former FBI agent, who specialized in court-ordered undercover break-ins, went on trial yesterday on federal charges of selling stolen diamonds, evading taxes, obstructing justice and persuading his friends to commit perjury.

H. Edward Tickel Jr., 42, who was fired after being indicted last November, had been an expert in picking locks, disconnecting burglar alarms and other undercover techniques used by the FBI in entering and bugging establishments suspected of involvement in organized crime.

Tickel, a 14-year FBI veteran, was acquitted by a U.S. District Court jury in the District last month of separate charges of trying to burglarize the FBI's credit union office at the J. Edgar Hoover Building.

At the start of Tickel's second trial in U.S. District Court in Alexandria, prosecutors sought to show that the former FBI agent was in North Carolina on Dec. 1, 1977 when a $200,000 jewelry theft was reported in the town of Lexington. The alleged theft is central to most of the criminal charges.

Tickel has denied repeatedly the charges and his lawyers contend the indictments stem from a "vendetta" conducted against Tickel by FBI officials as a result of his complaints about allegedly improper FBI practices, including failures to obtain court approval for surreptitious entries.