Fjestad, Zachary (August 17, 2010a). "Ampeg B-15N Portaflex". Premier Guitar. "the B-15 underwent constant change, and the B-15 was replaced by the B-15N in 1961. In 1962, Ampeg updated the B-15N with a solid-state rectifier called the B-15NB and introduced their famous “blue check” vinyl covering to their entire amp line. Ampeg went back to a tube rectifier and changed to a printed circuit board in 1964 (B-15NC). This model lasted until mid 1965, when they introduced the B-15NF with fixed bias tubes and a single-baffle cabinet. ... Ampeg went through numerous ownership changes over the next two decades with Unimusic taking over in 1967, Magnavox in 1971, and MTI in 1980. / St. Louis Music bought Ampeg in 1985 and finally returned some stability and respect to the brand. The company also reissued the B-15N Portaflex with blue check covering in 1995. Ampeg was purchased by LOUD Technologies in 2005, and in 2010, they introduced the new Heritage Series that is produced in the US."
