[sdiy] How to predict a transformer's current capability?

[Jaco Sloof]

well, i bought the transformer recently, just the block, but on the
sticker, it indeed states 220 v, but the hum won't be much of a
problem, i already built a separate "chassis-room" (maybe i'll use
some sort of lead-compound-enclosure as an add-on, whahah,
nuclear?hmm, the more weight, the better!(kinda funny, some people
think a machine works better if it it heavier)) to prevent any access
magnetic "radiation"(oh man, im deep into the STABLE psu thing :-> )
from leaking in the cables (inductance from leaky transformer)

the thing is, i have a nice block here, got the pcb, components on
the way, and i kinda tuned the stuff towards the transformer i
already have...
(72 VA, 2 x 2 A, 2 x 18 V, makes 32 Vct right)

so for the moment i'm gonna stick with this design, but yeah, you got
a point there with the 230 v input, i live in holland.. we had the
same raise here... so what does a 10 v raise in AC voltage really
affect? maximum power output? Current? Probably voltage on
secondary's, but i checked those and it say's 18.1 v ac.. nice and
tidy!
Maybe another spice run is in order... or some more advice from you
experts here...

in the mean time, i think im gonna put together an electromotor of 3
m utp-cable, some 1.5mm2 as axis-guidance (and half-turn-dc-injector,
kinda lost the word for it a.t.m), maybe running from my HP-Deskjet
Wallwart! heheh.... oh, some1 wants some schematics for that? oops,
going off-topic here, sorry...
> 
> Yes, toroidals - I don't use anything else anymore.
> 
> BTW, if your country's mains supply voltage has been raised in
> recent
> years (as it was raised from 220V to 230V in Germany), don't expect
> too much from salvaging transformers from old gear. They are very
> likely
> to produce excessive hum on today's higher voltage. The core is
> built
> for a certain maximum magnetic field, and nobody would have used
> more iron (bigger core) than necessary when the voltage was lower.
> (Well, some have, but that's the exception.)
> 
> You probably won't blow anything with an "outdated" transformer,
> but you're producing a much higher stray field which can induce hum
> into your circuits or even produce mechanical hum in the
> transformer.
> 
> I have replaced a lot of transformers in analogue synthesizers
> (230V,
> and mostly with a toroidal transformer), and cured a few hum
> problems.
> In a way, recycling transformers from old broken gear is the exact
> contrary ...
> 
> JH.
> 
> 


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