Weird Transformer

[spongebob]

Does anyone know how to connect a transformer like this one? It should have 2x 7.5V@3A on the secondary side, 220 VAC primary. Unfortunately it has no markings so I have no clue how to connect this thing. The red/black pairs on the right look like the 7.5V output, but why are there three connectors on the left (primary?) side?

If it helps, I measured resistance between the wires, it's 31.4 Ohm between red and black and 1.4 between yellow/green and yellow/yellow. I thought primary side has a higher resistance usually?? I'm confused... :?

Any ideas?

[Torchy]

Looks like two separate 110V/7.5V transformers on a common core. The primaries are wired a la centre tap to give 220V capacity.

[spongebob]

Hmmm this is strange, I'm pretty sure now that the right side is the primary side because I connected 28V AC (from another transformer) to the two yellow posts and measured over 130V on the black/red side!!!

So my guess was that I have to connect the mains voltage to the red/black wires. Result was a buzzing noise from the transformer, and I pulled the plug immediately...

Any other ideas how to wire this beast?

I know, I know...

[puretube]

connect the inner red to the inner black;
the outer red and outer black = 220V; (right side in pic)
the 2 yellow ones are the two 7.5V, (left side)
with the double blue = center-tap.

(Pollin?)

[spongebob]

connect the inner red to the inner black;
the outer red and outer black = 220V; (right side in pic)

Doesn't work, already tried that before, same result (buzzzz and trafo gets warm)

(Pollin?)

Yes (3â,¬), and by now I have gotten a response from their tech support: The two red terminals must be connected, and AC goes to the black terminals!! Weird configuration, but it works, it gives approx 9V AC between yellow and green.

I also bought their "transformer assortment" (for 2.50), a few kilo "Altmetall" would have described it better! :lol: Half of the stuff seems to be used, rusty and dusty, you get what you pay for I guess...