A 6X5 is rated to 70 ma current out. Zenith radios drew more than that. You are right one tube will operate the radio but you are exceeding limits of the tube. If you want to use a single tube best to use 6AX5. This one is rated to 125 ma. Tubes have the same basing.
Norm
:Hello all, First I would like to apoligise for mistakes I have made on this site. Just discovered it last month and my name has appeared with others comments. Anyway heres something to think about!!!!I have a Zenith 10S464 and it has 2 6X5 rectifier tubes. Why?? It will work just fine on one. I was repairing a friends and only had 1 tube, so rewired power supply and worked fine. Also on this radio has imputs for TV sound. How much earlier that June,1940 did radios have those jacks. Thanks in advance for all comments May not be able to reply