Much has happened since "The Forsyte Saga" was first shown here public television in 1969.

Not to the Forsyte family, thank God. No new Jolyons have been born while you weren't looking, and no more members of the family have decided to tell their spouses that they never could stand them.

But alot has happened to television saga-telling in those 6 1/2 years, and "Forsyte" starts its 26-episode run again today, at noon on WETA (Channel 26), not only as a successful re-run, but as the ancestor of a genre.

This is the continuing coffee drama.

America had the highly developed afternoon soap opera, in which housewives and their doctors get together over endless cups of coffee to discuss everybody's business, when Great Britain came along with the evening soap opera, in which historical and literary characters get together over endless cups of tea to discuss everybody's business.

The difference was not only the beverage and the serving time, but the budget. While American soaps get along with using that same old kitchen table set, along with the hospital reception desk and maybe a flowered sofa,* the British product showed rolling countryside, period furniture and silver tea services.

"The Forsyte Saga," the idea of which was to be taken up in "Upstairs, dowstairs," Masterpiece Theater pieces and other programs, was an immediate hit. In England, in the United States, even in the Soviet Union, where one actor dubbed all the male and female voices, people stopped going out so they could follow the staid adventures of this haute bourageois family from 1879 to 1926.

British vicars complained that the showings conflicted with church services - and most of them rescheduled the services. Here, Channel 26 took angry calls when it showed President Nixon's State of the Union message live in place of one of the episodes.

The appeal seemed to be that "Forsyte" and its successors were offering what high culture at the time was not: human drama about everyday life. The American soaps had that, too but they had not yet picked up the intellectual chic they are now acquiring, and the British products came with status.

You could call them history or literature, and you saw them at night , so you didn't have to explain that you were only home by your television set because you were sick.

Intriguing as they are, a cold look shows that they are not high drama. An awful lot of them consists of "How am I going to tell my wife?" or "Don't you think that love can be cruel?"

People generally grow expression less as they get older, and the sight of all that white powder that accrues in their hair - the series is filmed in black and white - is enough to give you a coughing fit.

But the greatest cultural contribution is the attempt to re-create the Victorian and Edwardian eras.

The Victorians were quite frank about some facts of life which we think vulgar and pretend don't exist. Questions such as conflict of classes, extended family obligations, the necessity of a couple to have money to live on before they marry, the contribution of discretion and emotional privacy to people's happiness - these are part of those daily teatime talks, and they are fascinating.

The fiction now in fiction is that the only true attitude is total "communication," that individual feelings have precedence over social or financial questions, and that class doesn't exist. This gives the coffee drinkers little to talk about outside of who is divorcing whom, leaving the delicacies of conversation to the tea-takers.

There are two ways of taking the current run if "The Forsyte Saga" - in daily or weekly doses. At noon, there will be a new episode shown every week day, so that you can start today you will be finished in just over five weeks.

If you want to take it more slowly, you have a choice of watching every Monday night at 10, or every Sunday afternoon at three. Starting by this method, either tonight or next Sunday it will, of course, take you 26 weeks.

In either method, no credit is given toward a degree in English literature.