A federal judge sharply questioned Rep. Mervyn M. Dymally (D-Calif.) here yesterday after Dymally testified he saw nothing irregular about members of the Black Hebrew religious sect using false names to obtain U.S. passports to enter Israel.

Dymally, a member of the House Foreign Affairs Committee who has pressed the Israeli government to legalize the status of Black Hebrews in that country, testified as a character witness for one of six Black Hebrews now on trial in U.S. District Court on charges of conspiracy in connection with an alleged welfare fraud scheme against Prince George's and Montgomery counties.

But during questioning, Dymally said he did not know anything about the charges against one of the defendants, Darlene Wilson, whom he said he met in 1983 or 1984 and who later worked as a volunteer in his reelection campaign. Dymally said he found her to be honest and her work professional.

When asked by Assistant U.S. Attorney John Stevens if his opinion would change if he knew Wilson used another name to obtain a U.S. passport, Dymally said he would not consider it to be significant.

"I'm very familiar with the complications arising from Black Hebrews' relationship in Israel and the necessity to get a passport to visit their family, and using another name is not unusual. In American life, stars, movie stars, songsters; everybody does it," Dymally said.

Chief U.S. District Judge Aubrey M. Robinson Jr., who is presiding over the trial and a second trial in which nine other Black Hebrews are charged with operating a multimillion-dollar crime ring, sternly questioned Dymally's views.

"Is it your understanding, congressman, that anybody can go to the U.S. Passport office and use any name they want to get a passport?" Robinson asked Dymally.

"Yes," the three-term congressman and former California lieutenant governor replied, "if you have a birth certificate or if you have legally changed your name."

But Robinson, continued, "You have to identify yourself and establish your identity, isn't that correct . . . . It doesn't make any difference if you're a movie star, congressman, federal judge, or whoever . . . . And you're in the Congress that makes that law, is that correct?"

"That is correct, sir," said Dymally.

Dymally seemed reticent to reveal who had asked him to testify, why he was asked to testify or who had provided him information about the charges against Wilson. He said he didn't "quite understand why she's here . . . . I've been told that she was indicted for making a phone call requesting information about welfare." He said he was not asked to testify by Wilson's attorney, but volunteered to appear, apparently after being contacted by a member of the Black Hebrews.

Claudette Johnson, a local business consultant testified Tuesday for defense attorneys in the other Black Hebrew case, in which a mistrial is being requested. Johnson said that she was assisting Dymally with the Black Hebrews and that she had attended many sessions in that 4 1/2-month-old trial to keep Dymally apprised of its progress.

Earlier this week, Dymally's former wife, Amantha Dymally, also testified as a character witness for Wilson.

Dymally said in a telephone interview after his testimony that he did not want to discuss the trial. "It took courage and commitment for a congressman to go to court and speak out for the Black Hebrews," said Dymally, adding that he realized that sounded self-serving.

"I am concerned about the Jews in Russia," he said. "I went there and visited them, the refuseniks, because I see it as an international human rights problem. I see the Black Hebrews under the same vein." Dymally would not discuss any efforts on behalf of the Black Hebrews but the British Broadcasting Corp. reported in January 1985 that Dymally met with Israeli Interior Minister Yitzhak Peretz about the Black Hebrews.

The Black Hebrews, officially known as the Original African Hebrew Israelite Nation of Jerusalem, claim to be descended from the original 12 Hebrew Tribes. They preach that the American way of life oppresses blacks and that through salvation they can be "delivered" to Israel.

The first Black Hebrews began arriving in Israel in 1969, a few years after Ben Ami Carter founded the group in Chicago. Claiming a right to enter the country under the Jewish Law of Return, the first emigres were allowed to enter by the Israeli government, which gave them permits, temporary visas and apartments in the Negev desert town of Dimona, which Black Hebrews now consider the "spiritual capital of the world."

By the time the Interior Ministry decided to bar further immigration a year later, there were several hundred Black Hebrews in Israel. Today, a third of the estimated 1,500 Black Hebrews in Israel were born in Israel.

In 1972, Israel's Supreme Court ruled that the Black Hebrews are not Jewish and therefore are not eligible for Israeli citizenship under the Law of Return. The group's status in the country has been in legal limbo ever since. Several former members of the group testified during the trial of the nine Black Hebrews that sect members continue to travel and emigrate to Israel, and that they often gain entry to the country using fake passports.

At least two former members said they were whisked away from this country to Israel as a way of avoiding criminal prosecution here for writing worthless checks for thousands of dollars worth of merchandise. They also testified that some of the items they purchased were later sold on the black market in Israel to help support the group's several settlements there.

Both said that they entered Israel on visitor visas, but did not leave when the visas expired. One former member, Alvin Scott, testified that he worked helping build a chemical plant near the Dead Sea and that he was paid lower wages because he lacked proper permits.

In 1973, fearing mass deportation, Carter ordered 78 of his followers to renounce their U.S. citizenship, and the United States has reportedly told those persons that they cannot return to this country. The group also established its own rump government, according to witnesses at the first Black Hebrew trial.

For the past decade, Israel has seemed unwilling to force deportation of the sect members because of the human rights controversy such a move might precipitate.

The most recent legal development involving the Black Hebrews came on June 25 when a three-judge panel of the High Court of Justice reserved judgment on an appeal by 46 Black Hebrews to overturn deportation orders.

The men and women had come from Black Hebrew communities in Dimona and Arad, also in the Negev, to Rehovot, in central Israel, to work in citrus packing houses.

They were charged with working without permits and with overstaying their visas.

Correspondent William Claiborne contributed to this report from Jerusalem.