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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