Thomas Organ/Vox engineer Brad Plunkett contributed a new low noise preamp circuit utilizing FET (field effect) signal transistors to the third generation V1154 Viscount combo amp. The photo at left shows the preamp board hinged to the open position, revealing large electrolytic capactors mounted to the back of the chassis that were used in the preamp power supply. The 25-5373-2 preamp circuit board was hinged in the chassis, allowing easy access to the bottom of the board for service. The "Repeat Percussion" area of the preamp board was left blank in the V1123, V1133 and V1154 as this feature was reserved for the V1143 Beatle.Ī zinc plated steel chassis enclosed the preamp circuitry and also served as the control panel. The list of features included in the V1123 Buckingham head, V1133 Royal Guardsman head and V1154 Viscount combo amp required that electronic components be installed into all but one of the modules in the 25-5373-2 preamp board. No electronic components would be installed in circuit board sectors where the channel or effect was not included with the given model. Thomas Organ would install electronic components only into the sectors of the preamp board that would be consistent with the features included in a particular amp model. Each sector supported a particular preamp channel or effect. The 25-5373-2 circuit board was arranged into sectors (see color coded diagram above). The 25-5373-2 circuit board allowed Vox to incorporate "modular" construction into their guitar amps in a new and innovative way. It consolidated all of the preamp and effects circuitry onto one compact and universal board given the Thomas part number 25-5373-2. The third generation preamp board used in the V1154 Viscount combo amp was designed by Stan Cutler of Thomas Organ. The preamp section used in the first (V-15 and V115) and second generation V1151, V1152 and V1153 Viscount amps utilized two or three modular circuit boards to support preamp functions, reverb and distortion. The only difference between the preamp section of the V1154 Viscount and V1143 Beatle amp was the inclusion of the "Repeat Percussion" effect in the V1143 Beatle. The preamp and control section used in the V1154 Viscount was identical to that found in the V1133 Royal Guardsman and V1123 Buckingham and similar to the V1143 Beatle. It also streamlined production through the use of a new universal preamp circuit board. Known as the V1154 Viscount, the new version introduced the use of low noise FET transistors. Thomas Organ, the US licensee and manufacturer of the Vox product line for North America, released the third generation of the Viscount combo amplifier in mid 1967. PC Board Layout and Circuit Design of the Vox V1154 Viscount Amp No use on online auctions, eBay or Reverb. © 1996 - 2023 The Vox Showroom, all rights reserved.
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