The consumption tax increase in April has had a negative impact on half-year financial results announced Oct. 24 by NEC Corp. and Toshiba Corp., the nation's two major electronics manufacturers.Despite increased exports supported by the weak yen, poor sales of personal computers and home-use electric devices, such as television sets, following the tax increase have had a negative impact on the first half of fiscal 1997, the two firms said. NEC officials said the price recovery in semiconductors contributed largely to its overall profit gains. NEC reported consolidated sales of 2.37 trillion yen, up 5.8 percent from the previous year, while its consolidated operating income increased 15.6 percent to 106.8 billion yen. The consolidated pretax profit of the 128 companies that make up the NEC group rose 7 percent to 65.2 billion yen.Toshiba Corp. reported 1.82 trillion yen in sales, but its operating income declined 49.4 percent to 28.03 billion yen. The company's pretax profit dropped 47.2 percent to 25.4 billion yen in the same period.The company said that PCs had suffered lackluster sales and a decline in prices. Home electronics devices such as television sets and air conditioners also suffered from a drop in prices, and this sector has seen its profit margin slim.NEC officials said that among its products, sales of communication devices such as cellular phones have increased 8 percent, while electronic devices such as semiconductors increased 14.9 percent in the first half of this year from the same period last year. Both shipment and sales revenues of PCs dropped, and computer sales dropped 20 percent to 385 billion yen.