[sdiy] A transformer question.

[Bob Weigel]

Tom,

Normally the variation in 20V around 230V divides to a variation of a 
coule volts in the stepped down side... and in most circuitry that's a 
tolerable variation.   And same percentage variation in the 110 to 
120...usually ok.  The 100V in Japan can cause some 'brown out' 
simulation, but some things will also work just fine with it.  For 
example a Siel DK80 I'm pretty sure wouldn't like the 100V without a 
step up transformer because the headroom is too limited on the 
regulators as I recall.  It'll buzz as the ripple drops below the 
regulator's headroom requirement.

You can get step up transformers for 100V to 120V.   For running Russian 
gear here I had a good sized 2X transformer so I just wired it up in a 
plastic box and made a simulation of the funny round pinned outlets on 
the top of the plastic box :-).  Anytime you have to step DOWN there are 
real cheap options out there.  Step up requires a more expensive 
solution.  -Bob

Tom Bugs wrote:

> Hi,
>
> A quick question about twin primary transformers for which I've not 
> been able to find answers...
>
> If there are twin 115v primaries.. (ie series for 230v and parallel 
> for 115v)
> - should this be able to cover Euro vs UK ranges of c.220v to 240v?
> - and would it cover US 120vAC and 110vAC in places like Cuba?
> - how can one deal with the 100v in Japan (other than replacing the 
> trafo with a different spec one?)
>
> I'd guess there's a bit more to it too - dependent on current draw, 
> trafo type & spec, etc..
>
> Any help greatly appreciated!
> Ta,
> Tom
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