+1 for always to either replace the filter caps or to power up any old gear softly.
Since the old caps usually open rather than short (permanently anyway), usually no other damage than a horrible mess of sticky and smelly electrolyte soaked paper shreds all around the innards though.
As cool looking as all these old tube contraptions can be, unfortunately IME the chassis is often the only salvageable piece, the rest is junk.
Cool looking junk, but still unusable junk.
As for Your find, just a wild guess, I'd say you're going to find either ~7V or ~13,5V on the outputs.
If everything works that is