Hammond 300BX 280VA 800V CT 300B Tube Plate & Filament Transformer

The 300BX is a high voltage (plate) and filament power transformer from the 300 Series, rated 280VA. It is aimed at builders, restorers and OEM engineers designing vacuum tube equipment who need a single transformer to supply the B+ plate winding and 3 separate filament windings. It is one of the two models in the series designed specifically for a particular tube: the 300BX is intended for 300B tube designs.

The high voltage secondary is 800V C.T. @ 288ma. RMS, with a 50 VAC bias tap on the high voltage secondary (with the C.T. grounded). The transformer also provides 3 filament windings: #1 5V C.T. @ 1.2A; #2 5V C.T. @ 3A; #3 6.3V C.T. @ 6A. The universal primary accepts 100, 110, 120, 200, 220, 230 or 240 VAC at 50/60 Hz; the units are designed to operate with both primary windings engaged. The 300BX can be run full wave bridge or full wave C.T.

Construction follows the series design: a Faraday copper primary shield (internally grounded to the end bell) reduces capacitive coupling from the primary and attenuates higher frequency current coupling to the secondaries, and concentric winding gives low stray field and low noise. The black powder paint finish matches the 1650 series of output transformers. Units are hipot tested at 2,000 VAC and are CSA certified (209651).

The 300BX uses the vertical ("X") mounting style; its outline is dimension reference X15 in the series specification sheet. Shipping weight is 12.1 lbs (5.49 kg). It is listed as REACH and RoHS compliant.