Hey Gang,
Whilst reading all the thoughts about DC filaments, something
crossed my mind. If we use say 6.3VAC as normal filament voltage and
switch to DC, wouldn't the DC equivalent for heating purposes be .707
times 6.3v = 4.5955VDC??? or have I missed something? Like maybe the
meter to measure the AC voltage becomes rectified DC then measured so
it is already converted to RMS? Hummm.
The reason I got thinking about this is that there are a lot of high
current 5VDC power supplies around surplus for cheep. Sure would take
care of that variable regulated current inrush problem with
3-500Z's/thoridated fills. Most of these supplies are variable from
about 2.5Vdc to 5.5Vdc and have current ratings that would handle a pair
of 3-500Z's fairly easily. Sometimes they are so cheep at the swap
meets you can get them for free when the swap meet is over just to carry
them off!!
The only problem I can think of is that with DC thru the filter
choke instead of AC from a center tapped fil transformer, where or how
do you make up for the lack of the center tap return?? Ground one side
of the filament leads?
Or have I gotten myself turned around here?
An inquiring mind wants to know...
Mike Baker K7DD
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