You can build a Cornet using the Hammond 370BX (instead of 270BX) power transformer for use internationally. The 370BX has primary taps for 100V, 110V, 120V, 200V, 220V, and 240V operation.
There is one slight issue
. The primary of the 270BX is rated at 115V, and is used at a nominal 120V. That means the Cornet design was optimized for this extra 4% output voltage. Or put another way, the 370BX will result in supply voltages 4% too low.
This is easy to fix
by changing R2 from 6.8k to 3.9k (1 watt) and R21 from 2.4 ohms to 2.0 ohms (5 watts). That's all there is too it. Happy soldering!