FINANCIAL MARKETS : 30-Year Bond Yield Falls Below 6%; Stocks Mixed : Markets: The Treasury bond figure, the lowest in more than two years, reflects a belief that the Fed will cut rates further.

Long-term Treasury bond yields closed below 6% on Thursday for the first time since 1993, as investors continued to lock in rates in the face of a struggling economy.

Just nine days after the Federal Reserve Board shaved its official interest rate for the second time this year, the bond market is clearly demonstrating confidence that the Fed must cut further, analysts said.

“There’s more evidence of a weakening economy coming in,” said Jim Kenney, government bond trader at Prudential Securities in New York.

But that evidence made for a mixed showing in the U.S. stock market Thursday, casting a pall over what is traditionally a strong period for stocks between Christmas and New Year’s Day.

In the bond market, the yield on the Treasury’s bellwether 30-year bond fell to 5.98% from 6% on Wednesday, marking the lowest yield since Oct. 29, 1993.

The T-bond yield, which affects rates on other long-term bonds and on mortgages, has tumbled from 6.33% on Nov. 1 as the economy has appeared to slow and as Republicans in Congress have pressed their battle with President Clinton for a long-term federal balanced-budget plan.

Many big investors believe that eliminating the federal deficit will help inflation and interest rates stay low well into the future by restricting government growth and freeing more capital for the private sector to use.

But the current downward pressure on bond yields is mostly a function of the weak economy, experts say.

The Conference Board on Thursday said its help-wanted advertising index slipped to 127 in November from 131 in October, indicating a weaker job market.

Separately, the New York district of the National Assn. of Purchasing Management reported that manufacturing activity in that region has slowed this month.

While lower bond yields stole the spotlight, short-term interest rates fell even more dramatically on Thursday. Those rates are most sensitive to the Fed’s benchmark federal funds rate, so Thursday’s slide was a strong vote of confidence that the Fed will soon cut its rate from the current 5.5%.

The yield on six-month T-bills, for example, slumped to 5.10% from 5.23% on Wednesday.

Some analysts cautioned, however, that thin trading and year-end portfolio adjustments could be exaggerating this week’s bond rally. Nonetheless, unless economic data shows a rebound in January, many experts see interest rates falling further.

Meanwhile, in the stock market Thursday, the Dow Jones industrial average eased 10.12 points to 5,095.80 amid increasing concern about the strength of corporate profits in the slower economy.

Cirrus Logic, a computer chip maker, helped trigger another sell-off in technology stocks after warning that current-quarter earnings could be as low as 13 cents a share, far short of analysts’ estimate of 44 cents. Cirrus blamed weaker-than-expected demand from personal computer makers.

“The PC consumer market hasn’t been as strong as we anticipated,” a Cirrus spokesman said.

Cirrus shares skidded 7 to 19 7/8. They were as high as 61 1/8 this year in the summer tech stock mania.

In the broad market, winners had a modest edge over losers on the New York Stock Exchange, but most stock indexes slipped with the Dow. The Nasdaq composite, heavily weighted with tech stocks, dropped 5.91 points to 1,042.22.

Analysts said the fading “Santa Claus rally” this week could be a warning for 1996. “As the old saying goes, ‘If Santa should fail to call, bears could come to Broad and Wall,’ ” said Frank Gretz, a technical analyst at Shields & Co.

But other experts say that as long as interest rates are falling, the bull market will remain intact.

Among Thursday’s highlights:

* Other tech stocks tumbling with Cirrus included Intel, down 1 3/4 to 57 1/8; Adobe Systems, down 3 to 61 1/4; Compaq, off 2 to 46 3/4; IBM, down 1 7/8 to 90 1/8; and Quarterdeck, down 1 1/4 to 28 1/8.

Also, Calabasas-based Tekelec slumped 5 1/2 to 10 1/4 after the maker of telecommunications test equipment warned that its fourth-quarter earnings will fall below forecasts.

* On the plus side, drug stocks showed new strength. Warner-Lambert gained 1 3/8 to 96 1/2, Abbott Labs added 1 1/8 to 41 3/8 and Pharmacia Upjohn gained 3/4 to 40.

* Some industrial shares also advanced, despite economy jitters. Air Products & Chemicals gained 7/8 to 52 7/8, Bearings rose 5/8 to 29 and Exxon added 7/8 to 82 7/8.

* Utah Medical Products jumped 5 3/8 to 20 5/8 after winning Food and Drug Administration approval to market its Cordguard II device, used to clamp and cut the umbilical cord to acquire uncontaminated blood samples after birth.

* Another big gainer was Los Angeles-based Chantal Pharmaceutical, which soared 4 3/8 to 27 1/2 on rising expectations for sales of its anti-wrinkle cream.

In foreign trading, Mexico’s Bolsa index eased 21.80 points to 2,790.76.