I have not followed this discussion as closely as others so please excuse me
for restating any obvious facts.
When you select the 250vac tap on the Ameritron transformer, you are not
generating voltages as if the AC line voltage was 250VAC. If the actual line
voltage is say, 245VAC then the voltages generated are 98 percent of the
voltages generated by a full 250VAC line.
The killer of tube filaments is over voltage so it seems smart to choose the
highest voltage tap that lets the equipment work. A slightly lower than
"perfect" filament voltage would serve to increase filament life as compared to
a
slightly higher filament voltage that would tend to decrease filament life.
For these reasons, I would also select the 250VAC tap when in doubt.
73,
Gerald K5GW
In a message dated 7/23/2007 7:59:13 P.M. Central Daylight Time,
jim@audiosystemsgroup.com writes:
On Mon, 23 Jul 2007 17:15:52 -0400, James M. Daly wrote:
>So needless to say I am left wondering what to think. Although my better
>judgment tells me to at least go the 245VAC route, if not Tom's (W8JI) full
>250VAC selection, despite what the guy at Ameritron said.
Tom is a very experienced RF engineer who designs amps. He does a lot of
science (that is, controlled experiments and study of the basic principles)
to
figure out what parameters really matter and which don't. Most guys who
answer
the phone for tech support are bench techs at best, and more likely minimum
wage flunkies. Looks like a no-brainer to me.
Like the man said -- you got great advice from someone who really knows.
Follow it and move on.
73,
Jim Brown K9YC
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