Tony Orlando, 33 years old and recently sick in the head, walks out of his dressing room at the Circle Star Theater wearing a huge, frightened smile for a shield. Hey Tony, cry the opening night photographers, and Orlando hesitates, quiet, blinking behind the smile.

"I'm noivous," he says.

He is considerably more than nervous. In fact he will tell you later that his knees are shaking so hard he is not sure he can remain standing. His feet feel sluggish. He has forgotten the second verse to his opening number. Last July Orlando stopped a show midsong, said he was ending his career, and burst into tears, and a few nights later he performed for the last time until his comeback during Thanksgiving week.

Last summer he was mentally ill, a manic depressive and about to break apart, but he didn't know it. Now he knows. He has told a press conference about it. Television cameras have filmed him talking about it. The National Equirer is about to hit the the stands with Orlando on the cover: I've Been to Hell and Back. After four months of psychiatry and lithium, the drug he says saved his cracking psyche, Tony Orlando has announced that he is about to try again.

A low drum roll rumbles up from the orchestra pit. Orlando leaps onto the stage, bends low in a bow, spins around and around with his arms out wide. He struts and laughs and throws them kisses and the theater full of almost 3,000 people, all the 10th-grade steadies and the ivory-haired ladies and the 6-year-old girls clutching roses for the star, the whole audience stands up and cheers.

And Orlando takes it in like sweet warm air, head back, eyes half closed. "The good Lord took care of me when I got a little ill," he says, "but boy did he take care of me to make sure I came to the right place to open it up again."

Brandishing his vulnerability. Saying over and over, in newspapers, magazines and television interviews: Yes, this business makes you crazy; I was a sick man to begin with; I got fixed by lithium and love. Orlando has come back some kind of show business survivor, patched and triumphant, and for this audience, at least, there's an idol on the stage.

The publicity that generated Orlando's "rebirth," as the National Enquirer referred to it, is clearly not going to do his career any damage, but Orlando says he's hoping to do formanic depressives what Betty Ford did for breast cancer victims - going public and trumpeting enconragement."I was in a position, finally, to make my illness a positive thing." Orlando says. "If anything. I want this to be a help to someone else."

Betty Ford, in fact, was in the audience Friday night when Orlando made his first appearance on the Las Vegas strip at the Riviera Hotel.

Eagerly, with the zeal of the newly enlightened. Orlando will rattle off the names of the greats who never knew they were manic depressives. Elvis Presley. Freddie Prinze. Marilvn Monroe, Abraham Lincoln. Theodore Roosevelt. Winston Churchill. Richard Nixon might fit in there somewhere too, Orlando suggests. He is carrying a disease that has taken heroes apart while the public looked on. Orlando says, and the pity of it all is that the heroes simply never understood.

So Orlando is telling a story now of three very sick years before his July breakdown, of an illness that festered inside him so long that when he finally cracked everybody except him knew he was in deep trouble. He was a big-eyed "Greekarican," with his two-woman backup duo. prancing across stage after stage: making the "Tony Orlando and Dawn" television show (two years in Nielsen's top 10. sometimes as No. 1); cutting "Tie a Yellow Ribbon" and nine gold records in all (60 million total sales); high stepping for the photographers with Betty Ford at his side.

A very big star. And a very sick man. At night he slept in a quivering fury, grinding his teeth and clutching the pillowease until the sheets were grenched with sweat. He woke up exhausted, whimpering, unable to move.

"I couldn't get to the bathroom." He is lighting a cigarette in a Las Vegas hotel room, the San Carlos engagement over. He is casually immaculate: mango-colored pants. V-neck sweater, thick black hair combed into place. He's a little overweight, and self-conscious about it; the lithium makes him retain water, he says. But never mind. "I welcome the 20 pounds - it was a ton off my mind." Calmly, with the detached wonder of a man astonished by his own history. Orlando is remembering life before lithium.

"It took me two and a half to three hours to get out of bed," he says. He would spend most of the morning working his way toward the floor; a foot extended slowly, then a hand; finally, holding the edge of the bed. Orlando would roll his legs off the matress. "I could not stand erect."

When he did reach the bathroom, usually by way of the walls furniture he knew he could lean on. Orlando would finish propping himself up. First it was over-the-counter calfein pills. "I'd take four vivarins before brushing my teeth." And after his friend Freddie Prinze committed suicide last January, it was cocaine, such frantic and enormous amount of cocaine that Orlando began hiding around the house the nasal decongestants he was using to clear out his nose.

And when Orlando was up, he soared. "The most superlative, most fast-moving, sharpest, wittiest state of mind you can imagine." He paced and smoked and spowed his dreams until the people closest to him became afraid of their health. He could talk for nine hours at a time furious, nonstop, the urgent voice demanding attention.

He thought up plots for television pilots with complete musical scores, and kept them in a folder labeled Ideas. He conceived a new kind of computerized typewriter that was going to make millions of dollars. He decided America needed a "Family Day," an annual observance in which great families - the presidential family, the King Family, the Osmond Brothers - would parade triumphantly through the streets, led by a wonderful stars-and-rainbow flag that would be put together at the Smithsonian Institution, on the same spinning wheel used by Betsy Ross.

Orlando was obsessed by "Family Day." He drew the flag on a pink cloth napkin. He felt the President should know about it. "I've got to call the President." Orlando insisted. And his wife, Elaine, who had married Orlando in 1964 and was now watching the workings of a mind she did not recognize, knew her husband was growing ill.

"If you got up to leave, he'd say. "You're not listening,'" Elaine Orlando says. "You couldn't disagree, and you couldn't escape." Orlando was exhausting her, living a fierce intensity that stopped only when his mood broke.

She would watch the elation snap, sometimes as Orlando was in the middle of a sentence. "Hey," he would say, the voice suddenly small. "I'm tired." He would drop into a chair quickly, legs buckling. Once in a while Elaine would hear a low mean from the dark, bent head, and then Orlando says he would just gaze at the floor, overwhelmed by his own inadequacy. "I'm a terrible entertainer. I'm not a good person. I'm not a good father."

Prinze's suicide began haunting Orlando's shows. His retarded sister had died two years earlier, and now Orlando was talking on stage about death and rellgion. On the morning of July 22, as Orlando lay in his hotel room bed before the evening show in Cohasset Mass, his music director, Robert Resairo, walked in and told Orlando he couldn't stand it any longer.

"He said he could no longer be associated with the things I was doing and saying on stage. That I was force-feeding my audience on religion and everything else, including Freddie Prinze's death, that I was pushing it down their throats."

Orlando walked on stage that evening with shiritails out and without his customary tuxedo. "You want to see truth?" he demanded before he went on. "I'll show you truth." He grapped the microphone and leaned low toward Rosario, close and dangerous. "Can we apologize?" Orlando was standing on the piano staring at Rosario. "Is it over, or can we apologize?"

Halfway through that performance he quit in the middle of a song. "All I really wanted to say was 'Help me, I would like to get off the stage to see a doctor." Orlando says. But he made it through the next few scheduled shows, and then on a late night television talk show Orlando heard a New York psychitraist describing his book "Mood Swing" about the symptoms of a manic depressive.

Orlando shook his wife awake. "I said, "Elaine, I know what's wrong with me, get this doctor, call him on the phone." And when the doctor, a Columbia Presbyterian Medical Center professor, Ronaid R. Fieve, met Orlando in New York a few days later, he recognized the disease almost immediately.

"He was in kind of manic exhaustion" recalls Fieve Orlando talked, joked, danged around his office, couldn't hold still. "An extremely high elated, expansive state - extremely witty, extremely charming he hadn't been sleeping for days on end."

Fieve put Orlando on lithium earbonate, the drug he has been prescribing for manic depressive patients, and peferred him to another psychiatrist for therapy. "We don't know how lithium works." says Fieve, "but it is believed that the drug somehow stabilizes genetic defects in the cell membrane of manic depressive patients," he says.

Whatever it does, Orlando says, it works. He began sleeping nights. His speech slowed down. He eased up on his intensive therapy, and learned to sense his body needs more lithium - "like a hummingbird's wings under the skin."

There are the beginnings now of a performer's schedule - three weeks in Las Vegas, a charity benefits in Los Angeles, probably some guest spots on television. Orlando would also like a movie - "I would love to be able to do a movie about a manic depressive." But there is also some uncertainty about Orlando's own limits, about how long it will take him to get back in shape - or whether the lithium will allow him to work at this frantic pace. In short, whether Tony Orlando's return to show business is permanent.

"He's a little hoarsa," says a woman at his Circle Star opening, her tone suggesting that chicken soup is perhaps in order. "But he's so sweet ."

And all through this first evening as Orlando eroaches and prances and exhorts the audience into a kind of summer eampfire enthusiasm [WORD ILLEGIBLE] - when I sing "One Day Happy [WORD ILLEGIBLE] part of the audience [WORD ILLEGIBLE] "Yaaaaaaaaay", the voice [WORD ILLEGIBLE] clearly not what matters anyway. He stop singing once, a breathless [WORDS ILLEGIBLE] between bars, and gaze around him at the flowers heaped up on [WORDS ILLEGIBLE] God." Orlando sighs. "I'm so happy to be back."