True, Jeff. Who knows when this radio was last regularly used or if they were running it with the lamp burned out. Perhaps it's no coincidence the 35W4 is a replacement from 1969 (or newer) whereas all the others tubes are original 1956 Motorolas.
So far I've not been able to remove the old lamp. Either it wasn't designed to be unscrewed or it's frozen after all the years. Did your zenith's light socket look anything like the picture of mine and if so, do you remember how to remove the light? Thanks.
