THE SENATE broke one tradition this week by allowing its proceedings to be televised. Now it ought to break another and pass a clean tax bill. The less the senators do to this bill, the better.

Senate tax debates have often been epics going on for weeks. But this time it's different. The Finance Committee tried several times to write a bill in the familiar way to keep the reform label yet to accommodate the interests that have traditionally prevailed on taxes in the Senate. It failed. Then it pulled back and, under Chairman Bob Packwood, tossed tradition aside.

This bill, unlike others in the past, has a limit on it: everyone agreed it could only give with one hand what it gets with the other; it has to be revenue-neutral. The idea of reform this time around is to pay for rate cuts by killing off preferences. At first, the Finance Committee tried to preserve so many preferences that it had no cuts to give. It finally went the other way -- a 27 percent top rate in return for wiping out whole volumes of preferences.

Now there is talk of restoring some preferential provisions on the floor -- the deductions for IRA contributions, business meals, perhaps state and local sales tax payments, a partial exemption for long-term capital gains. But the price for most of these is either internecine warfare (to help real estate you squeeze oil) or higher rates -- and low rates are the glue holding this bill together.

A lot of the issues will arise in conference anyway. Mr. Packwood made this point the other day in urging senators to lay off -- and he is right. Remember the considerable virtues of this bill. It would:

*Lift the tax threshold back above the poverty line, take millions of low-income families off the rolls, reduce the liabilities of others and generally restore tax burdens at that end of the income spectrum to about where they were in the latter 1970s.

*Shift the tax burden from individuals toward corporations, further restoring some of the balance lost in the corporate tax cuts of 1981, while also creating a credible minimum corporate income tax to keep so many companies from escaping scot- free.

*Sweep away most tax shelters by outlawing the paper losses that lie at their heart, while also wiping out the distinction between capital gains and ordinary income, one of the great complicators in the code. These are the price for reducing the maximum rate to 27 percent from the present 50.

You end up with a code that is several magnitudes fairer and simpler than the present one, much less of a distorting influence on the economy, yet perhaps an even stronger source of federal revenues. That's what the Senate needs to leave alone, lest it lose this good bill on the floor.