As befits a longtime backer of campaign finance reform Rep. John Brademas (D-Ind.) has always been fastidious about his own political funds, accounting to the penny for every receipt and expenditure.

With one exception.

During his 1974 re-election campaign, Brademas received an envelope containing 59 $50 bills from Tongsun Park, the South Korean businessman and Socialite. Brademas put $2,000 of the cash in to his office safe, and kept the other $950 for "incidental expenses" in the campaign.

Of the $950 in cash, Brademas says, he spent "$600 or maybe $700" on a dinner for political backers. He cannot document how the rest was used.

Most of this was legal. Brademas' campaign committee promptly reported the $2,950 contribution from Park, and it reported the disbursement $950 back to candidate Brademas. It was legal in 1974 to accept the contribution in cash. (Under a 1976 law, which Brademas sponsored, cash contributions over $100 are illegal.)

The committee's failure to report how the $950 in cash was spent, however, may have violated federal laws requiring itemized reporting of any campaign expenditure greater than $100.

The whole Park transaction was sharply out of character for Brademas, who ranks third in the House Democratic leadership.

The congressman says he has always believed that "cash contributions (See BRADEMAS, A9, Col. 1> are a bad way to do business." Except for this case, he says, he has paid his incidental campaign costs by check or credit card, "because with cash you have no paper record." Aides say the only other time in his political career he was offered a large cash contribution, he turned it down.

But in Tongsun Park's case, those personal rules were ignored.

That experienc seems to have been repeated by several members of Congress who had dealings with Park, who is currently described as the central figure in an effort by the South Korean government to but friendship on Capitol HIll.

House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.), who was guest of honor at lavish parties thrown by Park and accepted hundreds of dollars worth of gifts from the Korean, says he has not taken such largess from anyone else. Former Majority Whip John McGall (D-Calif.) says the cash gifts he took from Park were singular occurences in his political career.

Some members oif Congress - including some who were close to Park - have reputations among their colleagues for taking questionable money from many sources.

But the Korean affairs has also touched congressmen like Brademas, whose records seem beyond question - except for their dealing with Tongsun Park.

Why Tongsun Park?

Brademas, who has known Park for 15 years and who has attended a dozen or more of the Korean's parties, probably knows the answer better than anyone wise in Congress.

"He's charming," Brademas says.

"Lots of people in this city liked him a great deal. You would see Jerry Ford or Former Attorney General William Saxbe at his house, and I wasn't surprised. He could make friends in a very wide circle."

It was Park's charm and abiability, Brademas says, that made it difficult to refuse the $2,950 contribution, even though it violated Brademas' strong personal preference fror contributions, even though it violated Brademas' strong personal preference for contributions by check.

"It would have been . . . awkard, very awkward . . . to have opened right in front of him and complained that it was in green bills," Brademas, sayd. "I had known this man for some time. You don't do that."

Brademas also emphasizes that he knew the contribution was legal and that he had received non-cash contributions from Park in earlier campaigns.

"Under those circumstances," Brademas says, "it would have been inappropriate to complain about the cash." Since Park was a successful businessman, he adds, "coming from him, $3,000 in cash was not all that weird."

Brademas received the 1974 contribution on Sept. 23, after luching with Park downtown. As Park was driving Brademas back to the Capitol, he passed the congressman the thick sealed envelope, saying, "Here's a contribution."

"Come to think of it, I may not have known it was cash," Brademas said in an interview last week. "We didn't open the envelope until I got back to my office."

Brademas had been expecting a contribution from Park. Earlier in 1974, a Brademas campaign committee had rented Park's private club for a fund to return the rental fee as his contribution to the campaign.

The fee was $2006. Brademas says he does not know why Park's actual contribution was $2,950.

Brademas says he turned the money over to a secretary. She immediately gave him back $950, and put the remainder in an office safe for use as campaign petty cash.

The congressman says he carried the $950 two days later on a trip to California. When he took several political backers there to dinner at The Bistro, a posh. Los Angeles night spot, he says, he paid the bill between $600 and $700 inn cash. "I must have used the rest of the cash on various things on the trip," he said.

The Federal election Campaign Act requires itemized reporting of any expenditure over $100. Brademas' campaign reports show only a single entry for "incidental expenses" for the $950 of Park's cash that Brademas spent.

In every other campaign expenditure report since 1972, Brademas seems to have been meticulous in following the following the requirements. The reports show occasional disbursements to Brademas for "incidental expenses," All but the 1974 disbursement are fro relatively small amounts, such as $47.41 and $126.50, and Brademas says all but the $950 payment are documents to the penny.

James Mooney, Brademas' chief aide and custodian of his campaign funds, says the $950 was not itemized because Brademas was not used to dealing in cash in paying campaign expenses.

"I'd give $950 of my own right now if we could give the whole thing back to Park," Mooney says.

Like other members of Congress who fell into Parks ken, Brademas now rues his friendship withe Korean - and particularly the cash contribution. Because of it, he has been questioned FBI agents pursuing the Korean scandal. His name comes up time and again in reports about Park's operations.

From Brademas' voting record, it would seem that Park failed to win any influence for South Korea in his case. Brademas has been a critic of the South Korean government and has supported a reduction in American aid because of repressive practices there.

But Tongsun Park may have profited in other ways from his friensdship with John Brademas.

To increase his contacts on Capitol Hill, Park sometimes used his friends in Congress as bait to lure other members to his parties.

In response to Waashignton Post survey, Rep. Larry Pressler (R-S. D.), a member of an education subcommittee chaired by Brademas, recalled a party at which Brademas was the bait. Plessler said Park invited him to a party at which Brademas was to be the guest of honor, suggesting that subcommittee members ought to attend out of respect for their chairman.

Brademas says he was unware that he was guest of honor at any of the Park parties he attended.

In his written reply to a questionaire sent to all House members by the House Committee investigating the Korean affair, Brademas said that he never had any intimation that Tongsu Park might be working for the South Korean government, and that Park never made "any overtures to me on behalf of the government of South Korea . . ."

When FBI agents questioned him, Brademas said Park had taken steps to have him meet the South Korean ambassador to the United States.

"Park on one occasion indicated that it had come to his attention that the ambassador . . . was interested in talking to me." Brademas wrote in a memorandum summarizing his statements to the FBI.

". . . a member of the ambassador's staff subsequently called my office . . . I saw the ammbassador in my office in the Capitol on July 29, 1974."

That Park acted as an intermediary for the Korean ambassador did not surprise Brademas, the congressman said in an interview Friday. "He had a wide circle of contacts."

Indeed, Brademas said he is still not convinced that Park was ever an agent for the Korean government. "He may bave been just an aggressive businessman," the congressman said.