The Arlington County Board yesterday approved a $75 million deal that will shift control of the firm that runs Arlington's cable television system.

Officials of Arlington Cable Partners, which operates as MetroCable, said there probably will be a rate increase next year but not as a result of the deal.

Each year, rates have risen between 5 and 7 percent, according to county figures. Basic service costs $15.25 a month.

The deal, which cleared its final hurdle upon unanimous approval by the board, allows two of the current owners and managers of Arlington Cable Partners, Gustave M. Hauser and John D. Evans, to buy out the other partners for $75 million.

One member of the board sharply criticized the cable officials, citing numerous service complaints that have come to the county government recently.

"The letters we have received recently have been disturbing," said board member Mary Margaret Whipple. "They are sad stories. They are every homeowner's nightmare about trying to get things repaired. If I ran a business, I would be embarrassed."

Cable company officials attributed many of the complaints to mechanical problems associated with a $4.5 million upgrading that will increase the number of channels from 36 to 54.

"We're doing everything humanly possible to minimize inconveniences," said Hauser, who will own 80 percent of Arlington Cable Partners. He added that the channel upgrading is ahead of schedule.

The cable officials agreed yesterday to give customer refunds automatically if an outage lasts more than 24 hours and can be attributed to the firm. Currently, a customer must request the refund.

There was one outage in August that lasted longer than 24 hours that cable company officials attributed to unrelated construction in the Ballston area. Recent complaints have been about shorter outages, said Alice Foster, director of the citizens assistance and information department.

The firm last changed hands in 1983 for about $34 million, Hauser said. But he said the difference in the two figures should not be construed as profit.

"It's not the same cable system. We put a lot of money into it, including the upgrade," he said. Hauser declined to give a profit figure for the deal.

In other action, the board approved a request by the Trammell Crow Co. to build 344 units in three residential buildings near Washington Boulevard and Glebe Road. The firm and the Oliver Carr Co., which is developing another part of the project site, agreed to contribute $25,000 apiece to the county's housing fund.

The offer came after board chairman Albert C. Eisenberg made a last-minute request that the firm subsidize some units for poor tenants. "This is an opportunity for goodwill, good help," he said, noting the county's crisis in low-cost housing.

Adding that this was the firm's first project in the county, he said the subsidized housing would be "an opportunity for Trammell Crow to demonstrate its commitment to Arlington."