vac tubes / was Re: Schematics of Atanasoff-Berry
hilpert at cs.ubc.ca
Wed Sep 3 02:55:56 CDT 2008
William Blair wrote:
> Brent Hilpert wrote:
> > It has occurred to me that if one were setting out to build
> > a (small?) tube
> > computer today for fun, to look into selecting the primary
> > tube(s) from that
> > class; the question being if one would do any better than
> > just using
> > duo-triodes, which are in higher demand.
> That's exactly what I'm doing. The advantage of going with tube
> currently used for audio is that they are still in production,
> mostly in China and Russia. The disadvantage is that they cost
> quite a bit more. For small projects like mine, I have no worries
> about the availability of tubes that are no longer produced. For
> that matter, I suspect that even very large projects wouldn't
> have problems with tube availability considering how many of these
> out of production tubes are apparently still around. For instance,
> I can buy OOP 5BK7A dual triodes for US$0.78 each (I have ten on
> hand) or OOP 4BS8 dual triodes (to be purchased on my next order)
> for $0.38 each. The 5BK7A has a 4.7V heater and the 4BS8 a 4.5V
> heater. Either of these would work fine at 5V being outside of
> the typical filament voltage +/-10% rating only very slightly in
> the case of the 4BS8.
Great, you're already there, didn't realise from your earlier posts that you
were looking at such off-the-beaten-path tubes. I forgot there were so many
duo-triodes in that class with 4,5,8V,etc. filaments (don't tell the audio tweaks).
Make something using enough tubes and one can wire up the filaments in series
were intended for..
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