ON A NIGHT when fireworks were coming from all sorts of unexpected places in the Salt Palace, Mike Brown decided, well, why not him too. In 28 minutes of unexpected playing time last night, the 6-foot-9, 260-pound Jazz forward exploded for 11 rebounds, including six on the offensive boards, and 15 points,

leaving the Phoenix Suns wondering what hit them, and leaving the Jazz up two games to one in their best-of-five first-round playoff series.While the Jazz played about as well as they've ever played in the playoffs in the 107-98 win, Brown rewrote his own personal playoff record book. He had career highs in points and rebounds and minutes-played.

It came so smoothly that you'd have thought Brown has these kinds of nights all the time - when in point of fact he'd never had a playoff game like this, or even a playoff season. Coming into this year's playoffs, he'd had four trips to the playoffs to his credit - with the Chicago Bulls in 1987 and 1988 and with the Jazz the past two years. In nine total games during those four years he'd played 85 minutes and scored 18 points and 12 rebounds - about the same as what he got last night in one fell swoop against the Suns.

"I was lucky," he said, in partial explanation, "Mark (Eaton) got in foul trouble a lot earlier than normal. I had to step in. My role is to help a lot on defense and get emotional. That's what I did."

When Brown spelled Eaton and got six points and six rebounds in eight minutes of playing time in the second quarter, the Suns were wondering why they'd bothered getting Eaton out of the game in the first place.

When Eaton was whistled for his fifth foul early in the fourth quarter, the Suns got their final dose of Brown. The result was the same as before, only more decisive. With the score 93-88 and a game that had been one streak after another looking for one team to come up with the streak that would win it, Brown came through with four points in a 33-second span of time.

At 2:10, seeing 6-foot-4 Jeff Hornacek guarding him because of a defensive switch, Brown broke for the hoop, leaving Hornacek no choice but to foul.

"This is a little guy guarding me," explained Brown. "I'm just going to slide down the middle and see what I can get. They shouldn't have switched."

He made both of his free throws to put the Jazz up 95-88. Then, after Dan Majerle missed a shot on the Suns possession, Brown, taking a pass from John Stockton, scored on a baseline jumpshot at 1:37 that put the Jazz up 97-88. After that, it was all over but the Suns' hacking. The Jazz would make just one more field goal, and eight straight free throws, to pull away, and to pull into Thursday's game with the ball really in their court.In Game 3, the Jazz left little doubt in pregame introductions just whose building the game would be played in. After ordinary introductions for the Suns' starters, the house lights were turned off, leaving the only light coming from the glow of 10,000 green and purple glow-in-the-dark rings handed out at the door. Then came real 4th-of-July type fireworks from the Salt Palace ceiling, and sparkler-style fountains spraying out of the 24-second clocks above the baskets.

As the Jazz starters were introduced by spotlight, the remainder of the $2,500 worth of fireworks were shot off. The Jazz's pregame plan, obviously, was if you have the homecourt advantage, flaunt it.

Curiously, the explosive start seemed to motivate the Suns, who led at the end of the first quarter by eight, and who maintained that lead three minutes into the second half.

At which point, Guess Who drilled a 15-foot jump shot that keyed a Jazz run that closed the gap to three points. Then, at the end of the half, it was Brown, again, coming in to replace Eaton, who made a dunk to trigger a 7-points-in-55-seconds run that sent the Jazz into intermission with a four-point lead, 51-47.

"I had to give the fellas a spark," said Brown, who said that, yes, there were nights in previous playoff years when he wondered when his time (read: minutes) would come.

"Waiting for it for a while, that makes this all the better," he said. "I've always felt hard work will pay off in the end, if you just keep hanging in there."

His production last night far exceeded his 1990-91 regular season averages of 4.8 points and 4.1 rebounds a game. So did his 28 minutes exceed his regular season average of 17 a game. "It helps to be in there," said Brown. "Then you have time to make things happen." Today, the Suns are aware of that as he is. At first they thought it was good he was in the game. But the longer he stayed, the more they wished they'd left well enough alone.