Have a Narrator where the AM seems to be working very well. The FM side has very little volume. On the back are 4 terminals. Left to right D J blank and antenna . The J and the non labeled ones are connected by a piece of metal on the back. What are the "D" and "J" for? Would connecting a FM antenna give me more volume? Or, could it be a tube going bad, etc?

"D" and "J" are the FM dipole antenna connections. Try connecting an external FM antenna to these two terminals and see if the FM band improves. If not, the problem could be a bad tube; especially the second IF amp tube, which is only used in FM mode. But the most likely problem is that the set needs a good external antenna to work well for FM.

Also..check the FM alignment if the other things mentioned by CV don't work.

I don't think that I've seen one of these old sets that didn't benefit markedly from an FM alignment. Generally it transforms a working set from an insensitive "dog" to a high performer. I suppose that after 60 or so years the components have drifted enough to shift the circuits slightly off the resonance peak set at the factory.

:"D" and "J" are the FM dipole antenna connections. Try connecting an external FM antenna to these two terminals and see if the FM band improves. If not, the problem could be a bad tube; especially the second IF amp tube, which is only used in FM mode. But the most likely problem is that the set needs a good external antenna to work well for FM.
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Thanks.