Hammond 278CX 454VA 800V C.T. High Voltage Power Transformer

The 278CX is the 454 VA unit of the 200 Series, delivering an 800V centre-tapped high voltage secondary at 535 mA alongside a single 6.3V C.T. filament winding rated 6A. It is intended for tube power supplies that need substantial plate current from a 115 VAC, 60 Hz North American supply, and it has no second filament winding.

Mechanically, the 278CX is an enclosed, 4 hole, chassis mount design in the vertical ("X") mounting style, with minimum 6" long leads. Ordering-table dimensions are A 3.75 in (95 mm), B 5.00 in (127 mm), C 4.56 in (116 mm), D 3.00 in (76 mm) and F 3.81 in (97 mm), and the mounting slots measure 0.20 x 0.38 in (5 x 10 mm). The shipping weight is 12.5 lbs (5.67 kg).

Hammond states that 200 Series units can be run full wave bridge or full wave C.T., use Class A insulation (105 degrees C), are Hi-Pot tested at 2,000V RMS and are CSA certified (209651). The part is listed as REACH compliant and RoHS compliant.

The primary is rated 115 VAC, 60 Hz. For 115V input the series notes call for the White and Gray primary leads with the Black taped off, and on the 278CX specifically the Gray wire is actually BROWN. Where roughly 125V line voltage gives too high a secondary, the White and Black leads are used instead. Never power both the Gray (Brown) and Black leads at once.