Evans & Sutherland Computer Corp. had net earnings of $1.33 million or 16 cents per share for first quarter 1989, up from earnings of $1.02 million or 12 cents per share for the same period last year.

Sales for the quarter were $25.16 million, a 12 percent decrease from sales of $28.25 million for the first three months of 1988.First quarter net earnings included a $1.10 net extraordinary gain from the repurchase of convertible debentures. First quarter 1988 earnings included $297,000 in extraordinary gains.

David C. Evans, president, attributed the decrease in the sales from first quarter '88 to the change last year to the emphasis of the Graphics Products Group. During the quarter, Evans & Sutherland repurchased some of its convertible debentures at a discount and sold some of its appreciated holdings in the common stock of Adobe Systems.

Evans said orders are running ahead of plan in the Simulation Division, thus increasing the "healthy backlog." He said technology developments are proceeding well, and several new business opportunities for high-performance visual systems are being pursued.

In the Computer Division, Evans said sales of existing graphics products are on target, the new Conceptual Design and Rendering System is ready to be delivered, and sales of the new molecular modeling software from Tripos Associates, a wholly owned subsidiary, "are very strong, both in the United States and abroad."

Evans said development of a new supercomputer is going well, "and software tests have yielded excellent results." He said several letters of intent for the supercomputer have been received and that the probability of midyear deliveries is "good."