John-Boy is a grandfather!

No, not really -- the grandfather is actually Richard Thomas, and an actor is not the same as the character he plays. Moreover, Thomas, who played John-Boy Walton for just seven years (an eon in TV time), is in his 50th year as a stage actor, and it isn't fair to epitomize such a long career with one role.

Not that he regrets it: "I'm very proud of that show," he says. "It did a lot for me -- gave me leverage. And I had a blast."

But in the long, lengthening shadow of that famous role, Thomas, 56, has built up an admirable body of stage work, heavy on the classics. He has become the kind of dedicated actor who could be a mainstay of our national theater, if we had a national theater to showcase such a career.

Thomas brings that career to Heinz Hall this week, playing Juror No. 8 in Reginald Rose's famous courtroom drama, "Twelve Angry Men." No. 8 is the lone holdout who gradually convinces the other jurors to re-examine the evidence. It's generally been the star part, played memorably in the 1957 movie by Henry Fonda and in TV, movie and stage versions before and since by Robert Cummings, Jack Lemmon and Boyd Gaines.

Thomas' stage career began at age 7 in 1958 on Broadway, as a replacement in the role of John Roosevelt in "Sunrise at Campobello." But as a child he also did a lot of TV. "I kind of grew up with TV, live, in black and white, but I did theater right along," including three more Broadway plays in the 1960s.

Moving to California in the late '60s, he did a series of movies before starting "The Waltons" in 1971, but even in those "Waltons" years he kept doing theater, such as a "Saint Joan" in Los Angeles.

"I'm not a snob; I do it because I love it. If you forget about the money part and the sweet seduction of being seen by millions, most actors who do both prefer theater."

Thomas talks fast, articulately, ideas bumping into each other as they rush out. ("Yes, I talk faster than my kids can follow," he laughs.)

"I like working on film," he admits. "It's highly detailed and challenging." And he has continued working on the screen, logging more than 40 TV movies in his long career.

"But I'm a stage animal. I like playing through from beginning to end; I like the camaraderie and the demands of playing sophisticated texts. If you're lucky enough to play good parts, you have writing you can look up to rather than play down to. You get to stretch up."

Thomas has played many great parts, including Hamlet and Richard II. In Hartford, where for several years he had a working partnership with noted director Mark Lamos, I saw him play Peer Gynt, and in Washington, D.C., with wunderkind director Peter Sellars, the Count of Monte Cristo.

Clearly he relishes the challenge of these famous roles. "In all those great heroic parts, you have to devastate yourself. Eight Hamlets a week aren't easy -- I've even done nine, counting the student matinee. Basically, out of eight performances, depending what standards you hold yourself to, you'll do three you're proud of, a couple that will serve and a couple you wish no one had seen."

Most recently in New York, Thomas played Touchstone in Lamos' "As You Like It" in Central Park and appeared in "A Naked Girl on the Appian Way" for the Roundabout Theatre, producers of "Twelve Angry Men." He also spent a half year as East German spy Gunter Guillaume opposite James Naughton's Willy Brandt in "Democracy," which initially kept him from doing "Twelve Angry Men." When it was being cast, he'd already committed to "Democracy," and the plays were on Broadway at the same time: "I'd walk by their theater and think, 'I'd like to be in that one, too.' " So he was all the readier to commit when he was offered the tour.

Surprisingly, given Thomas' dedication to the stage, this is his first national tour. Last year, "Twelve Angry Men" played 19 cities and there are 19 more on tap this year, starting up in Lexington, Ky., then Tampa and San Antonio before reaching Pittsburgh.

He says he loves it. "If you're an actor, you live out of suitcases anyway. Being a traveling player is authentically romantic, with a new audience in a new town every week, setting up, doing the show, finding a good bar, trying not to get into any trouble."

He also loves the play, which he describes as "just 90 minutes, a short ride on a fast machine, with 13 actors carrying the weight. It has a high level of difficulty, a fast ensemble play like basketball or hockey. That's exciting."

He calls it "a show that generally speaking wives don't have to drag their husbands to see." It's about a courtroom process we know even more about than at the time of the original 1954 CBS TV Studio One show or the 1957 Sidney Lumet movie. "We've become a nation of jurors with cable shows and reality TV."

Thomas thinks the script comes back into its own on stage, since the original live TV version was based on theatrical dramaturgy: "It was always a play."

He grants that they often play in large theaters. Some have been as small as 1,200, as on Broadway, but they've gone up to the 4,500 Fox in Atlanta, and most are around the 2,700 of Heinz Hall. "That's one of the challenges," he says. But although intimate, "Twelve Angry Men" is also "a big show, with 12 actors on stage at a time. It's basically one scene with great forward momentum. It really galvanizes an audience."

Thomas' grown children by his first wife live in California, with those grandchildren. He lives in New York with his second wife and their son, who sometimes visit him on tour. Not seeing them is "the hardest part of touring." But tours of good plays, as opposed to musicals, are too infrequent to pass up. "A good paying gig in a production you love? This confluence of commerce and art is rare."

In this way, as in his willingness to do good roles at regional theaters, perhaps Thomas is part of a national theater -- the American, decentralized version. That's where, he says, "Twelve Angry Men" belongs.