[hpsdr] OT HV power supplies

[Chris Smith]

Hi Chris

The original EDSAC was probably powered from the 250V DC mains that was available in that part of Cambridge back then.

There are no notes about the power supplies and no circuit diagrams either.

There hasn't been a decision made about the PSU yet but it looks, from the few photos which have survived, that each rack had its own unit at the foot of the rack.

We think each rack probably draws 1-2 amps at 250V DC and the whole machine 20 amps so constructing linear supplies would need either one very heavy transformer or 20 smaller but still pretty hefty ones.

SMPS seemed the 'simpler' way to go.

Thanks

Chris

On 5 Jun 2012, at 04:38, Chris Albertson wrote:

> 
> > I'm looking for a supplier of SMPS with a nominal 240V AC input and 250V
> > DC o/p at 1 to 2 amps. Anyone know where I can find one? I was in contact
> > with a company in India but that seems to have fallen off the radar!
> >
> > This is required for a project to build a replica of EDSAC the computer
> > built at Cambridge Uni Maths Lab in 1948/9.
> 
> 
> Are you using SMPS because you need to save power and run cooler.  I'd have to ask "why bother" if you are building a vacuum tube computer.    It would be easy to build a linear supply.  I think you might be able to use a common isolation transformer.   These are easy to find in any size you need.   they have 240VAC output and then the CRCRC filter can drop it some to the required voltage with the two series resisters.   I'd bet this is how they did it in 1948.   The SMPS will be electrically noisy unless you take care to make it not so.
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California


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