I don't see a power transformer, this has the early series tubes... 25L6, 25Z6, 6xx, etc. The big ST tube is probably the ballast, which soaks up the remaining line voltage (the tube filaments add up to 74 volts).
I looked it up the 6230 on Nostalgia Air and found a battery set... but the right one is there if you scroll down to the 4th page...
here