solid-state 'Harvard' amps (one with reverb), which were 15W practice amplifiers. Design-wise the tube amplifiers were quite different from their predecessors, as the active tone controls and blending distortion circuit had been removed and the latter feature replaced by a crude version of the channel switching concept. A new feature addition was a crude insert-style effects loop. II Series and the Rivera Era The II Series amplifiers were produced from 1982 until 1986, being the last Fender amps to be made at Fullerton. The specifications for these amplifiers, and leadership of the design team, came from Paul Rivera (then marketing director) and are known as Fender Rivera era amplifiers. Some amplifiers in the series used the II moniker; the Champ II, Princeton Reverb II, Deluxe Reverb II and Twin Reverb II, while others such as the Concert and Super Champ did not. Many of these amps had the normal Fender clean sound and in addition a switchable mid voiced gain channel, designed to compete with the Mesa Boogie Mark Series series amps that had gained popularity at the time. The tube amps in the series feature hand-wired eyelet board construction and are also becoming sought-after collectors items, due to the design and build quality. The range included one small tube-driven bass amp, the Bassman 20. There were also some solid-state amplifiers using the II moniker, such as the Harvard Reverb II. Other solid-state amps produced during the Rivera era included the Yale Reverb, Studio Lead, Stage Lead, London Reverb, Montreux, and a solid-state issue of the Showman. Many of these units shared the same circuitry boards in one capacity or another. Red Knob The Red Knob amplifiers were produced from 1987 until 1993. They were made in Lake Oswego, Oregon, at the Sunn factory, a brand/company that Fender had purchased in 1985–86. These were some of the first models produced by the newly formed Fender Musical Instrument Corporation. Aside from the bright red controls, these amplifiers have a slightly similar appearance to the older Blackface cosmetics, bearing black control panels with white lettering and the late 1970s "scripted tailless" Fender logo. Many of these models were simply refitted with black knobs and early 1970s "unscripted tailless" Fender logos in 1996 when most Fender amplifier manufacturing moved to the Ensenada factory in Mexico. This series of amplifiers all used printed circuit board construction. Two utilized the same circuit board and wattage,