The KE77003-B tube mains transformer, which is a modern version of Williamson's specifications from 1947, has the following design parameters:

Primary windings (170VA):
- 2X115V@50Hz (Imax=0.95A)
Secondary windings:
- 2X350V@0.15A (Imax=0.3A)
- 4X3.15V@4A (Imax=4A)
- 5V@3A (Imax=4A)
Miscellaneous data:
Dimensions/Weight: 57X120mm/1.5kg
Total primary resistance: 7 Ohm
Total HV secondary resistance: 86 Ohm
Effective std rectifier drive impedance: 16+43=59 Ohm



KE77003-B, Roger's Mains Transformer

Which makes the transformer useful as:
- Standard Williamson mains transformer using RC-filtered silicon bridge rectification (440Vdc@0.15A, each channel).
- Mains transformer using boosted Williamson configuration with KT88/6550 (somewhat lower dc & heater voltage)
- A spare 5V/3A winding for optional nostalgic 5V4/GZ34 tube rectifier usage, 300B heating or logic supply.
- Low cost alternative: 125USD

More info:
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KE77003-B, Taps