CONNECTING POWER:
As any other vacuum tube amplifier, Model 1 needs two voltages for proper operation: (1) Plate, or Anode voltage, Va and (2) Heater, or filament voltage Vf. Plate voltage should be brought to the terminal block J80 and filament voltage to J90. Picture below shows the layout detail with J80 and J90.
Plate voltage (Va) should have nominal value of 250V (acceptable range is
PCL82 tubes are designed for series connection of their filaments, so they require current source (as opposed to some other tubes that require voltage source for filament supply). Heater specification for this tube is 0.3Amp and 16V. Rugged construction of the tube’s heater allows that it is powered from the voltage source as well, but you can expect high current surge and bright yellow heater in the first few seconds of operation. In theory, this reduces life of the heater, but these tubes are very rugged and will have long life even in this less than perfect situation. Basic version of the Model 1 amplifier has the two heaters connected in series, so the filament supply needs to be able to provide 32V at 0.3A. Resistors
Filament voltage can be DC or AC, so there are no polarity markings on J90. If the DC is used, left pin is the system ground (see the Figure above), so the negative polarity of the filament voltage can be connected to that pin, although doing opposite will not affect operation, as long as filament supply is independent of plate supply.
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