A receptacle includes an electrically insulative bottom wall, and an electrically insulative upright wall upwardly extended from the border of the bottom wall, the upright wall having a back wall portion corresponding to the rear side of the bottom wall. The bottom wall is adapted for mounting at a circuit board or electronic device to hold a transformer in such a manner that the lead wires of the primary winding of the transformer are disposed at the front side of the bottom wall; the insulated lead wires of the secondary winding of the transformer are extended over the top edge of the back wall portion and then turned downwardly and bonded to the circuit board or electronic device.