International Bank, the Washington corporate conglomerate, reported its first quarter profits climbed 29 percent to $4.8 million from $3.7 million and operating revenues increased 24 percent to $7.1 million from $5.7 million.

Sharply higher quarterly earnings were also posted by Tech Serv Inc., of Beltsville, which earned $83,000 in the quarter ended March 30, compared with only $2,300 in the same period a year ago.

Most of the gains reported for the quarter ended March 31 by International Bank resulted from IB's acquisition of minority interests in three major subsidiaries last December. The company issued 5 million shares of new stock to buy out the minority shareholders, and as a result, earnings per share declined to 39 cents from 51 cents a year ago.

Profits were down for IB's industrial subsidiaries, but because the holding company purchased minority interests in some of those companies, IB's share of their income increased to $2.5 million from $2.1 million.

Buying a bigger stake in a property and casualty insurance company also contributed to a 90 percent increase in earnings from those operations, to $2.9 million from $1.5 million. Income from life insurance subsidiaries increased to $761,000 from $619,000, while earnings from finance and leasing operations fell to $115,000 from $158,000.

Earnings of the company's international operations -- which include overseas banks -- plunged to $67,000 from $868,000; IB officials said half the drop was due to converting transactions in foreign currencies into dollars, and the remainder was caused by soaring interest rates.

Tech Serv said its profits took off when it resumed production in January of flying model targets used for military training. Sales for Tech Serv's third quarter, ended in March, increased to $766,000 from $458,000 in the same period a year earlier.

The $83,000 profit for the quarter helped erase losses earlier in the year, putting Tech Serv into the black for the first nine months with a profit of $5,600 (a penny a share) from operations plus earnings of $48,000 (9 cents) from sale of property. A year ago the company lost $8,000 (2 cents) in the first nine months.