Charles J. Cedeno, who claimed he was fired last year as Fairfax County's purchasing director for "daring to expose" contract irregularities, has been charged by Philadelphia authorities with 19 counts of bribery allegedly committed while he was in charge of purchasing for that city's transit agency.

Cedeno, who now works for a private company, was arrested yesterday at his home in the community of Marlboro in Monmouth County, N.J. He was later released on $25,000 bond.

According to Philadelphia authorities, Cedeno was fighting their attempts to extradite him. If convicted on all the counts, he faces up to 133 years in prison.

The bribes allegedly took place while Cedeno was purchasing manager for the Southeastern Pennsylvania Transportation Authority (SEPTA), a position he held from 1973 to 1979, the year he took the Fairfax job.

According to law enforcement authorities, Cedeno attracted the attention of the Philadelphia district attorney's office after SEPTA's general manager reported widespread "rumors and vague allegations" that a businessman known as "Ten Per Cent Marty" allegedly had made payoffs to win contracts with the agency.

After an eight-month investigation, a Philadelphia grand jury recommened that Cedeno be charged on the bribery counts.

Howell K. Rosenberg, chief of special investigations in the Philadelphia prosecutor's office.l investigations said yesterday the grand jury alleged that Cedeno had accepted $15,500 in bribes from four businessmen who sold various supplies -- nuts and bolts, cleaning agents and electric parts -- to the transit agency on a nonbid basis.

The four businessmen, who cooperated with authorities and were not charged, are Martin Tartacoff, secretary-treasurer of Peerless Fastener Products Inc., who allegedly paid Cedeno $4,000; Malcolm Fairmount Motor Products, who allegedly paid $5,000; George Domers, co-owner of Eagle Electric Co., who allegedly paid "a couple of thousand," according to Rosenberg, and Marvin Hart, president of Raymond T. Green Co., who allegedly paid $5,000.

According to Rosenberg, the alleged payoffs amounted to 2 to 5 percent of the total value of the nonbid contracts awarded by Cedeno.

Cedeno was hired by Fairfax in 1979 after an extensive executive search and screening process. Before he wasd employed, the county made an extensive check of his background that included sending a police investigator to Philadelphia.

"Some things just don't turn up," said Fairfax board chairman John F. Herrity, commenting on the case yesterday.

Cedeno triggered a brief but explosive controversy in Fairfax in June 1980 when he claimed he was asked to resign as director of the county's $70 million-a-year purchasing program after he had uncovered a pattern of irregularities and mismanagement in contract awards.

Count officials denied Cedeno's allegations, saying he was fired for using "significant vulgarities" and creating "an atmosphere of fear and disgust" in the purchasing department.

A criminal investigation of Cedeno's charges, requested by the Fairfax board, failed to result in prosecution. Cedeno sued the county for $1 million last August, but dropped the suit last December after the county withdrew its dismissal notice and permitted him to resign.

Cedeno then went to work for ATPA, Inc., a company based in Skokie, Ill., that supplies buses for Latin American companies. Cedeno apparently was employed by ATPA at the time of his arrest yesterday in New Jersey, but company officials refused to comment.

Cedeno could not be reached for comment yesterday.