Tom,
Sorry, but you're avoiding my point. IF the current is adequately
limited, where's the problem?
If the current is not limited, all bets are off, your argument is
perfectly valid (using 'argument' in the philosophical sense of putting
forward a theory), and, on my part, there's no disagreement.
Interestingly, a number of Marconi professional tx's used the series
filament arrangement with an 'equalising wire'. Said wiring was done
with a twisted pair of thick multi-strand conductors (in brown wire,
'cos company colour code used brown for fils and heaters!) from each
tube back to the transformer. The transformer had carefully matched
windings, and several thousand Tx's of different models have been turned
out, with no problems that I've heard off, using this method for
4-125As, 4-250As and 4-400As.
Personally, I would have used 2 matched, centre tapped filament
windings, and connected the centre taps together. I don't believe the
cost would be higher, by much, if at all.
73
Peter G3RZP
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