A coalition of Northern Virginia Democrats and civic leaders have formed a defense fund to help Charles W. Rinker Jr., a Democratic Party activist and former official of Youth Pride Inc. accused of misappropriating U.S. funds from three low-income housing projects.

Rinker, 41, a Methodist minister who is chairman of Virginia's 10th District Democratic Committee, pleaded innocent on Wednesday to the charges, which capped a 2 1/2-year investigation into the activities of Youth Pride and its spinoff organizations in the District of Columbia.

Fund-raising appeals bearing the letterhead of the Charles Rinker Defense Fund and the signature of nine prominent Northern Virginians, including state Sen. Clive DuVal II (D-Fairfax), were sent this week to more than 1,000 community activists and friends of Rinker.

"It was just sort of a spontaneous thing," said Joan Allen, a member of the Arlington Planning Commission who spearheaded the defense fund and helped draft the letter. She said she hopes the group will raise between $10,000 and $15,000.

"As individuals we just don't feel Charlie is capable of wrongdoing," said Amy Appelbaum, former chairman of Arlingtonians for a Better County, a good-government organization that endorsed Rinker in his unsuccessful 1979 bid for a seat on the Arlington County Board.

"The next several months will be hard for Charlie and Lora Rinker," said the letter. "Very few people would have the tens of thousand of dollars Charlie's defense is likely to cost."

The former secretary-treasurer of P.I. Properties, Rinker is charged with making false statements to the government and with authorizing company bank transactions that allegedly were used for the personal expenses of other alleged conspirators, including P.I. Properties director Mary Treadwell.

Rinker faces a maximum penalty of five years in jail and a $10,000 fine on the conspiracy charge and the same penalty on a charge of mail and wire fraud.

Rinker, who left Youth Pride in 1978 and now operates a consulting firm to help low- and moderate-income tenants get loans and home financing, has said he worked for Pride out of a desire to promote social justice and never suspected wrongdoing.

Rinker said yesterday he expects his legal fees will run between $25,000 and $100,000. "Potentially it's a horrendous amount and of course I don't have that kind of money.

"One of my fears after the indictments came down was that people were going to drop away or run the other way when they saw me. My spirits are generally very good because so many people have called and written," he said.

Earlier this week Rinker took a leave of absence from his position as chairman of the Democratic committee. "It seemed to me that every time I would make a statement as chairman of the 10th District the media would report, 'Charlie Rinker is one of five people indicted in connection with Pride.' I didn't think the party or our congressional candidate, needed that."

Besides Treadwell, who has her own defense fund, and Rinker, codefendants in the case include Treadwell's sister, Joan Booth; Treadwell's estranged husband, Ronald S. Williams, and Robert E. Lee Jr.