EDSAC lives

William Donzelli wdonzelli at gmail.com
Mon Dec 1 08:31:53 CST 2014

> I do wonder about the logistics one would run into doing a machine the size of the ENIAC. Maybe there's more NOS stuff out there than I realise, but sourcing 18000 tubes and associated components is different than a few hundred. Granted, you don't have to build out the full complement of accumulators.

Building a complete ENIAC replica would indeed be hard. If only exact
proper NOS parts were used, I might just say impossible. As always, it
seems, one can blame the capacitors. Even the micas from the 1940s -
and I mean the good mil spec ones - are starting to fail in large
numbers. I am not sure what ENIAC actually used (my guess is a mixture
of papers and micas), but I might thick modern types stuffed into
vintage cases would be the only reasonable route. Getting NOS paper
and micas from the era is not hard, but they are at best only a step
or two away from the trash can.

The tubes might not be too bad to source, if the project could stand
using used, tested pulls. I do not think any of the tube types in
ENIAC are rare types (if someone out there has a list of the 20 or so
types they used, please post it), regardless of what the audiophiles
think. I might even think that I could even source a majority
percentage out of my stock.

Original wire would be hard to stock in such quantity, but there are
some vintage reproductions that could be obtained. Sockets, resistors,
connectors - not much of a problem, given time.

Finding original relays might be very difficult to find in NOS, or
even good, used condition. I do not know what type ENIAC used, but
finding exact vintage replacement relays for any project can be a hair
pulling experience. If the relays needed are "telephone" types, that
would be a plus, as modifications could be made due to their modular
nature. I would not want to be the guy in charge of that project.

Transformers - that may be where all the money goes. Once again, I am
not sure what they used, but big plate and filament transformers are
getting quite pricey. I suppose there may be luck involved if the
ENIAC used massive transformers for the plate voltages for the
thousands of tubes, as the audiophiles would have no need for those,
but if used off the shelf 100 or 200 Watt or so - ouch.


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