Frank (Buddy) Geoltz Sr., 71, was back at Columbia Country Club in Bethesda last week, hitting against the practice backboard where he is a regular fixture even though he retired in 1971, after 33 years as the club's tennis pro.

He had been away for a month on an annual odyssey to renew his reputation as the scourge of the geriatric tennis set, this year, on successive weeks at East Providence, R.I., Evansville, Ind., and Charlottesville, Va., he collected the National 70-and-over singles titles on three surfaces gras, indoors and clay.

Goeltz, a 5-foot-8, 168-pounder with dancing gray eyes, has won 33 national titles in singles and doubles since retuning to tournament competition in 1969, when tournaments previously restricted to amateurs were opened to pros. Since 1971, he has complied an awesome record in events for "Super Seniors" - players at least 65 years young.

In 1971, he became the first to achieved a "Grand Slam," sweeping the National 65 singles on grass, hard courts, clay, and indoors. He also won all four titles in doubles. Last year he moved up to the 70s and slammed again. He might have repeated this year, but opted not to spend $800 on a one- tournament West Coast trip and skipped the Hard Courts in California.

A Goeltz walked from the tennis shop to the men's grill at Columbia on Friday afternoon, the fist man he encountered said warmly, "How you doing, Pro Congratuations." Everybody he passed had similar greetings.

Goeltz was nicknamed Buddy as a youngster in his native Wilkes-Barre, Pa. But around Columbia, where he is "Tennis Professional Emeritus," nearly everyone calls him "Pro."

"That started after I had been here about 10 years," Goeltz recalled, "because my technique looked so smooth, so relaxed in the execution."

Seemingly effortless, efficiently compact and maddeningly disguised shots characterize "the Goeltz techniques," a style of tennis that discards most of the traditional thinking about stroke production and footwork.

Goeltz's self-taught technique eliminates the backswing and follow-through, emphasizing racket balance and body balance instead. His theories, based on a few simple physical principles elaborately refined to cover every aspect of the game, are fascinating.

"Many persons think I'm a crank, a screwball," Goeltz admits, but he is sure of the logic of his approach and he teaches it enthusiastically.

Certainly it has worked splendidly over the years for Goeltz, who took up tennis in 1917 after the mayor of Wilkes-Barre replaced the local baseball diamond with four courts.

Goeltz won his first junior tournament in 1922, his first adult tournament in 1930, and played in the U.S. Nationals at Forest Hills, N.Y., for the first time in 1932. The same year, he says, he introduced another radical innovation - short pants - to U.S. tournaments.

At the time Goeltz was in the trucking business and played tournaments only two months a year. In 1938, after considerable indecision, he took the pro job at Columbia.

He has a storehouse of anecdotes about the decade when he played occasional pro trounaments against other coaches and the few touring pros of those days, including such all-time greats as Bill Tilden, Fred Perry or Don Budge.

He played Tilden three times, and remembers disdainfully, the ways "Big Bill" tried to con and intimidate him in the few sets that Goeltz led. "You don't even belong on the same court with me," Tilden screamed at Goeltz, who had been hard of hearing since childhood, in their first meeting.

"I would have given my right arm to beat that son-of-a-bitch," said Goeltz, who has a much higher regard for the other stars he played. "If you made a good shot against them, they nodded," he recalled. "Not Tilden. When you played him, only he could make great shots. But I'm sure his egotism was part of what made him the greatest player in history."

Though always a competitor at heart, Goeltz's greatest contributions's were as a teacher, and his pupils include an impressive list of regional and national champions. "From a simple game, I learned philosophy and psychology," he says, "and I came to appreciate how much I don't know. Knowledge makes you a humber person."

Goeltz lived within walking distance of the club for 26 years before moving in 1966 to Rockville, where he resides with his wife Anne and the oldest of their five children - Buddy Jr., 35, who succeeded him as the pro at Columbia and now teaches at the Gaithersburg tennis center operated by brother Bobby, 30. Buddy was an area champion. Bobby win the National Interscholastic title a record three consecutive years for Landon School and starred at Princeton, and daughters Cynthia, 33, Suzanne, 36, and Heidie, 21, are all fine players.

"The most gratifying thing about my job is that I lived so close to the club and the schools that I was with my family when the children were growing up," Goeltz says. "I never made a lot of money but I've had an interesting life.

"When I retired and decided to go back to playing tournaments, a friend of mine told me I was crazy.He said, 'Why don't you relax?' But I told him, 'I don't want to die on the vine.' If you stay active, you're not going to get old so fast," said Frank Marion Goeltz, a remarkable man.