Hammond 166J25B 25 VA 25V CT 1A 117V 50/60Hz Power Transformer

The 166J25B is a low voltage/filament power transformer from the Hammond 166 Series, supplying a 25 VAC center-tapped (C.T.) secondary rated at 1 A for a total of 25 VA from a single 117V 50/60 Hz primary. It is intended for designers, OEM engineers and repair technicians who need a compact, open style transformer that bolts straight to a chassis.

Unlike most of the 166 Series, which is wound for 115 VAC at 60 Hz, the 166J25B is one of the versions rated for a 117 VAC, 50/60 Hz primary, so it can be used on either line frequency. The secondary is center tapped, giving access to the midpoint of the 25 VAC winding.

Construction is open style with a channel bracket and two-hole chassis mount, and the transformer uses a dual bobbin design, so no electrostatic shield is required. Leads are a minimum of 6 in long. On the drawing schematic the primary leads are black and the secondary leads green, with a green/yellow lead on the center tap. Insulation is Class B (130 °C) for extra protection, while the design is UL listed as Class A (105 °C).

Overall dimensions are 3.25 in (83 mm) (A), 2.00 in (51 mm) (B) and 2.00 in (51 mm) (C), with 2.81 in (71 mm) between mounting holes (D) and 0.19 in (5 mm) mounting holes. The part drawing gives the same measurements more precisely as 3.25 in / 82.6 mm (A), 2 in / 50.8 mm (B) and 2 in / 50.8 mm (C), with 2.81 in / 71.4 mm hole-to-hole spacing and 0.187 in / 4.7 mm width-wise mounting holes. Shipping weight is 1.35 lbs (0.61 kg).

The design carries a hi-pot test of 2,000 V RMS, and the series is UL listed and CSA certified. The 166J25B is also listed as RoHS and REACH compliant.