[sdiy] Strange transformer behaviour

[Karl Ekdahl]

I've found a couple of pcb transformers that has four
windings, two primary and two secondary. The two
primary windings has 3kohm / 2kohm resistance and the
secondaries has 70ohm/100ohm resistance (no center
tap). 

I connected my 220v to one of the primaries (i think
the 2kohm) and measured the outputs on the
secondaries, i got ~20v on each. I thought this was a
little bit strange behaviour since the secondaries has
different resistance...

..Well, to the problem, after rectifying (single wave
rectifier) and adding a 1000uF cap, the ~20v turned
into a 40v (!) output! I suspected i would get
something like 23v and i need something around 20v but
i only get 40v and that is too much. Is this correct
behaviour?

Happy for any thoughts...

/Karl

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