In the second case of its kind in a week, two California residents and a Hong Kong businessman were indicted yesterday on charges of illegally exporting sophisticated U.S. electronic equipment that administration officials said could be used in Pakistan's nuclear weapons program.

U.S. Attorney David F. Levi said Arnold I. and Rona K. Mandel and Hong Kong importer Leung Yiu Hung were charged with conspiracy, illegal exports and false statements. The indictment returned by a federal grand jury in Sacramento, Calif., alleges that the illegal exports were made to Pakistan through Hong Kong between July 1982 and August 1983.

The exports, which the government charged were made without valid licenses, included oscilloscopes and sophisticated computer equipment made by Tektronix Inc. of Beaverton, Ore., which alerted the government because of the high value of the shipments and was not involved in illegal acts, Levi said in a telephone interview from Sacramento.

In late 1983, a Dutch businessman acting as purchasing agent for the Pakistani nuclear program was arrested in the Netherlands for illegally seeking to obtain a sophisticated oscilloscope made by the same Oregon corporation, according to Leonard S. Spector, a nuclear proliferation expert at the Carnegie Endowment for International Peace.

On July 10, a Canadian citizen of Pakistani origin, Arshad Z. Pervez, was arrested in Philadelphia on charges of seeking illegally to export special steel for the Pakistani nuclear program. Court records said Pervez also made inquiries about obtaining beryllium, which is used in nuclear weapons detonation.

State Department spokesman Charles E. Redman said yesterday that U.S. Ambassador to Pakistan Arnold L. Raphel had expressed serious U.S. concern Thursday to Pakistani President Zia ul-Haq about the Pervez case, which has imperiled U.S. aid to Pakistan. A 1985 U.S. law bars aid to any non-nuclear country such as Pakistan that seeks illegally to export U.S. material or technology for its nuclear weapons program.

Raphel "was assured that the government of Pakistan is taking this matter as seriously as we are," Redman said.