[morzh]

Ed

I don't know if the radio is for 110/117V and you might have 120V, so some bucking might be in order, but Zenith is known for using smaller transformers than the rest, so it might be natural for it to get warmer.
Again, it is an old radio and probably should not be driven hard

Another way to deal with it, a quiet fan, 12V or so, exhaust or blow doesn't matter. Aim it at the hottest part, although general circulation action is also helpful.