SEMI-TECH Group has paid 30.24 million deutschemarks (about HK$136.6 million) to increase its stake in German industrial sewing machine maker GM Pfaff from 51 to 72 per cent. Last month the company paid 91.8 million marks to take control of the troubled firm. Pfaff turned over 1.04 billion marks last year and made a net loss of 18 million marks. Semi-Tech chairman and chief executive James Ting said: ''We are happy to make the additional investment, which averaged a 20 per cent discount to our first purchase. ''Meanwhile Pfaff has begun its restructuring in earnest.'' Since taking control of Pfaff, the group has arranged the sale of Singer to International Semi-Tech Microelectronics for US$850 million.