The power amp driver transistor (Q4) was designed to increase the gain in the preamplifier audio signal. Power Amp Driver Circuit - The driver circuit included two transistors and a driver transformer. The 12 watt power amplifier circuitry for the V1011 Pathfinder had two stages: driver and output.
Pathfinder amp series#
The main supply voltage was 31 VDC but two series resistors in the power supply provided additional power taps at 27.5 and 18 VDC. Two additional 500 uf capacitors provided additional smoothing. Primary DC smoothing was accomplished by a large, vertical 2500 uf filter capacitor.
Pathfinder amp full#
The power supply for the V1011 Pathfinder utilized a full wave rectifier using two diodes and a power transformer with a center tapped secondary. Several of these unused traces were adapted for use in the E-Tuner circuit that was added to the V1022 Pacemaker and the V1032 Cambridge Reverb in 1967. I suspect that this area of the board might have been under consideration for the future addition of a "Distortion Booster." The unused area of the 25-5274-2 PCB resembles the individual Distortion Booster circuit board ( Thomas part number 25-5277-2) installed in the V1141, V1131, V1151 and V1121 preamps. It is also worth noting that Thomas Organ designed some unused circuit traces onto one end of the 25-5274-2 PC board. The reverb and MRB sectors of the modular PC board were empty (see photos and diagram above). The modular design of the 25-5274-2 PC board allowed the electronic components related to MRB and reverb circuits to be omitted. The Pathfinder did not include either MRB or reverb. The Pathfinder offers an excellent example of how this modular construction technique was implemented. Given the Thomas part number 25-5274-2, this single circuit board consolidated all of the preamp, tremolo, reverb and power amp circuits onto one circuit board.
Thomas developed a single printed circuit board that would be used in the proposed solid-state Pathfinder, Pacemaker, Cambridge Reverb and the Berkeley II amplifiers.
Thomas Organ then aimed their efforts at an efficient modular strategy for building their smaller amps. Adding the 120 watt RMS power amp module to the universal three chanel preamp section formed the Super Beatle. When the preamp section was combined with the 60 watt RMS power amp module, the Royal Guardsman and Westminster arrived. When the universal preamp section was combined with the 30 watt RMS power amp module, the Viscount and Buckingham amps were created. Thomas then developed 30, 60 and 120 watt power amplifier modules to combine with their new universal preamp section. This circuit board was given the Thomas part number 25-5222-2. Thomas Organ engineers devised one modular strategy for building their higher powered solid-state guitar amps and a second modular strategy for their smaller solid-state guitar amps.įor their larger amps, Thomas developed a universal preamp printed circuit board (PCB) that would form the basis for a modular preamp and control section for their higher powered amps. This style of construction allowed electronic sub-assemblies to be shared by multiple amplifier models. Vox amplifiers, Thomas engineers aimed for manufacturing efficiency through modular construction and standardization. In late 1965, faced with the task of rapidly developing an entire range of solid-state U.S. Thomas Organ Designs the US Vox Amp Line Using Modular Construction and Standardization Techniques The power amp heat sink was suspended beneath the main chassis to facilitate air circulation and fastened to the pan with three machine screws. The germanium output transistors and the T1 power amp driver transformer were mounted to the power amp heat sink. The third part of the chassis was the power amp heat sink. It was fastened to the top of the chassis pan with two machine screws. The second part of the chassis was the control panel, including theĬontrols, jacks and switches. This basic chassis pan was also shared with all models of the solid-state Pacemaker, Cambridge Reverb, Vox Berkeley II, Berkeley III and Vox Scorpion amplifiers. It also supported the T2 power transformer and the 2500 uf main filter cap. It housed the 25-5274-2 printed circuit board assembly. The stamped and formed steel chassis pan was the backbone of the chassis. The chassis was comprised of three pieces: the chassis pan, the control panel and the power amp heat sink. It was offered from 1966 through 1971.Ī single steel chassis housed the all of the preamp, power amp and power supply circuitry for the Pathfinder amp. The V1011 Pathfinder was the entry or "student" level solid state amplifier from the Vox division of the Thomas Organ Company of Sepulveda California. No use on online auctions, eBay or Reverb. © 1996 - 2023 The Vox Showroom, all rights reserved.
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