1R5 can be used as a direct replacement when pin #5 isn't connected directly to B+. In Zenith G500 series it goes through a 68K resistor which is ok.
1R5 will operate on broadcast band and some lower frequency short wave. It won't operate on higher frequency short wave bands used in your Zenith.
Norm
: Can a 1R5 be used as a direct replacement for 1L6 in this set.