I'm building a single tube 3-500 6m amplifier around an OEM SB1000
transformer. The Heath transformer is dual input 110/220VAC with HV,
filament(5vct), and 12VDC secondaries on the common primary. The
original design of this transformer wound to accommodate the 3-500.
The problem is that the filament secondary appears to be overly high
and measures 6.5VAC no load and 6.09vac with the tube installed. Since
there's an exponential loss of tube life with only minor filament
overvoltage, I'm caught between a rock and a hard place. In this
instance, the obvious answer is to install a dedicated filament
transformer correctly designed for the application; however, that
involves an additional (redundant) component. The question is whether
it's somehow practical to reduce the filament voltage without getting
involved with an odd ball low ohmage, high wattage resistor series
installed on the secondary. Any comments would be appreciated. Ron
W2CQM/3
.
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