INDIANAPOLIS, Ind. (AP) _ Anacomp Inc., a computer services company, has reduced by $31 million to $383.9 million the price it will pay to acquire disk-drive maker Xidex Corp., the companies announced Monday.

Indianapolis-based Anacomp, the nation's third-largest supplier of micrographics products behind 3M Corp. and Eastman Kodak Co., had announced July 12 that it would pay $10 for each of Xidex's 41.5 million outstanding shares.

But Monday, the companies said that under a definitive agreement approved by the boards of both companies, the new buyout price would be $9.25 cash per share, reflecting further negotiations since the initial agreement.

Anacomp expects to begin a tender offer no later than Friday, the company said.

Xidex rose 12 1/2 cents to $9 a share in national over-the-counter trading Monday, while Anacomp fell 12 1/2 cents to $9.12 1/2 a share on the New York Stock Exchange.

In announcing the merger agreement earlier this month, Anacomp had indicated that Xidex, based in Santa Clara, Calif., was well managed and made a good business fit.

Xidex, which has posted losses for two straight years due to writeoffs on acquisitions, is a leading manufacturer of computer data storage. It controls 25 percent of the world floppy disk market and also makes computer output microfilm, microfilm readers and reader printers.

Anacomp, which employs more than 3,000 people, is a supplier and manufacturer of services and products based on micro-imaging technology known as micrographics.

Xidex has 7,000 employees worldwide, about half in the San Francisco Bay area at factories in Santa Clara, Sunnyvale and Fremont. It also operates factories in Irvine; Omaha, Neb.; Iron Ridge, Wis.; and Wales, Britain.