Maximus wrote:
Two 6 volt lantern battieries connected parallel - positive to positive and
negative to negative and the positive lead to the positive terminal on the
connector, and the negative lead to the negative terminal . I don't remember
the part number of the adaptor, and I returned it. It fit into the hole
properly but evidently did not connect right with soemthing. The line cord
does not disconnect from the radio. It says 13.8 volts on the back of the
radio but the PDF for the radio says 12 volts.

Ever see a bird get annihilated by an exploding insulator g ?

When the trees hit the wires around here the explosion echoes impressively
throughout the entire valley, the sky lights up like Phu Bai during incoming
and of course the lights go out LOL.
snip

OK, if you had the batteries in parallel, it would still be 6v - and the
radio wants about 12.

Try them in series.