Virginia Gov. Charles S. Robb came home to Fairfax County last night to "recharge my batteries" and to exhort the nearly 500 county Democrats who gathered for this year's annual Jefferson-Jackson Day fund-raising dinner.

"This is my committee," said Robb, Fairfax-bred and the state's first governor from Northern Virginia since 1918. Robb used the occasion, which raised about $10,000 for local races this fall, to remind the crowd that he will propose his first budget next year and will need all the help he can get in the General Assembly.

"In the next session . . . I'll be proposing initiatives that will require thoughtful, dedicated public servants," Robb said. "I will count heavily on the return of all delegates." The Democratic-controlled Senate is in "good shape," Robb told the crowd, but more must be done in the House to "shore up the size of the delegation," he said.

Robb has attended the Fairfax fund-raiser in years past, but this was his first visit as governor and the only local Jefferson-Jackson dinner he has attended this year, according to county Democrats.

The throng included Lt. Gov. Dick Davis and retiring state Sen. Adelard Brault as well as the 31 county Democrats running for one seat or another this fall. "I knew we had a depression," Davis joked from the podium, "but I had no idea so many people were seeking public housing in Richmond in 1985."

Robb did not mention his recent nomination of black Richmond lawyer John Charles Thomas to the state Supreme Court, but Fairfax Democrats needed no reminder.

"We think it's great," County Democratic Chairman Dottie Schick said before the dinner began. "It shows that in Virginia the Democrats really do care."

"It's such an encouraging action," former U.S. representative Herb Harris said of the appointment. "This shows the real ability of Democrats to think and act independently. It's so hard for us up here to understand some of the deeply ingrained attitudes in the southern part of the state."

And because the presidential election is just a little more than a year away, the evening was not devoid of loftier notions. Tables in the hallway of the Tysons Holiday Inn were filled with buttons and flyers from each of the Democratic presidential contenders. The daughter of Sen. John Glenn (D-Ohio) was present working the crowd in behalf of her father. And, as has become the rule at gatherings attended by Robb, there was talk of a national candidacy for him in 1984.

"I hesitate to say what I'm really thinking," Sen. Brault said to applause, "and Lynda Robb please keep your seat . . . . I may very well be introducing a man who will be occupying the White House before too long."