I recently started working on my old battery sets. I discovered something in the grid circuit of the IF tube. It looks like 2 "saucer shaped" discs stacked together in a little clip. I am guessing it is some sort of battery? It measures about 300mv..Does anyone know what I have here..this is a 1941 set so I don't know how this "battery" could still have a voltage? Does anyone know of a good reference book on old battery sets?

:Hello, sounds like you have a radio that used bias batteries. Very little current was drawn from these batteries so they lasted quite a while. There is a web site that describes these but I cant remember where it was....yet
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:I recently started working on my old battery sets. I discovered something in the grid circuit of the IF tube. It looks like 2 "saucer shaped" discs stacked together in a little clip. I am guessing it is some sort of battery? It measures about 300mv..Does anyone know what I have here..this is a 1941 set so I don't know how this "battery" could still have a voltage? Does anyone know of a good reference book on old battery sets?

:I have found the article on bias cells..here it is.
:http://members.aol.com/caschwark/biascell.htm
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:I recently started working on my old battery sets. I discovered something in the grid circuit of the IF tube. It looks like 2 "saucer shaped" discs stacked together in a little clip. I am guessing it is some sort of battery? It measures about 300mv..Does anyone know what I have here..this is a 1941 set so I don't know how this "battery" could still have a voltage? Does anyone know of a good reference book on old battery sets?