Fort Worth, Texas-based Tandy Corp duly make its biggest personal computer announcement since it entered the business a decade ago yesterday, topping the list with the 80386-based Tandy Model 4000, at a very competitive-sounding $2,600, which compares with the $4,500 or so industry analysts had been expecting. Few details of the new products were available yesterday, but the company also announced its first Personalike lap-top, the Tandy 1400 LT, and two additions to its low-end 1000 family as well as an 80286 board for existing Tandy 1000 computers. The 80286-based Tandy 3000 has a faster chip and the company cut its price.