transformer question

[tam]

hello everyone.
i found a transformer (at a second hand store) and i thought ill ask before aplying voltage to it and burn it... (like i did before... :oops: )
anyway ,its a center tapped, and the secondaries mark 15v-0-15v.
but the primaries has _4_ inputs! and marked something like that:

1_____
2_____  110v~
3_____   50H
4_____  110v~

now, i measured resistence, and i get around 70 ohm from 1 to 3 and from 2 to 4.

any sugestions?
thanks.

[Peter Snowberg]

Hola Tam

Your transformer sounds like it has dual primaries for use with either 110 or 220 volts.

This is how I would assume it is wired:

For 110V you would wire one AC input to both pins 1 and 2; and the other AC input goes to pins 3 and 4.

For 220V you would wire one AC input to pin 1; a jumper wire connects pins 2 and 3, and the other AC input goes to pin 4.

I am assuming the polarity of the windings with the above information. It might be that for 110V the inputs go to pins 1 & 4 together and 2 & 3 together or for 220V the AC lines go to pins 1 & 2 while a jumper connects 3 & 4.

I would start by connecting a jumper from 2 to 3 and then attaching AC to pins 1 and 4. You will either get the stated voltage from the secondary, or you will get almost nothing. If you get nothing, reverse the connections for pins 2 and 4.

[tam]

hola peter!
i conected ac to pins 1 and 4 with a jumper on 2 and 3- and got the right voltage, but after like 10 seconds, smoke started coming out of the transformer... :lol:
ill try to reverse the polarity...

[tam]

now im conecting ac(220v) to pins 2 and 3 and a jumper conecting 1 and 4.........good voltage.........but smokiee again.. :lol:
also now im reading 70 ohm with any configuration on the pins?!(1 to 2 or 3 or 4 ,2 to 3 or 4 etc.)
creo que no tengo mas opciones...cheers

[niftydog]

second hand store you say? Hmmm. Was it just sitting there by itself? Does it look used? I'm thinking it's dead-ski.

70 ohms seems kinda high to me. And 70 ohms accross all terminals is definately a bad sign.

[tam]

second hand yes.....
its like an electronics shop - where they have this carton box on the floor with used (and new) transformers....most of them without specifications...
they also sell rectifiers that has been taken out of wall warts....(the little pcb with 4 diodes and a cap....)and all kinds of stuff like that.dont try to ask them for a pt2399 :lol: