I have an old Sanyo cassette recorder, model M 1540A. Can find no information on what polarity of tip it uses. Only know that it's 6.0 Volt. No markings on outside of case to show what it is. Sanyo website and customer service has no information and websearches come up empty.
I have opened the unit. It takes 4 "C" cell batteries. The circuit board is old and isn't labeled. I can't tell how the AC adaptor jack is wired to the board. A label on the outside says to use AC Adaptor6CV120 or 6CV121.
I have two adaptors I am considering using with it, both positive tip. One is a class 2 transformer that outputs 6V DC and 300mA. The other (much bigger)is labeled AC Adaptor and outputs 6V DC and 2000mA.