you can get 7 pin from oade, possibly oade board, sonic sense, sonic studios, possibly this board in yardsale section, possibly ebay.
regarding power form batts. you're using the sled right? contacts on sled clean? no corrosion? sled really should only go in one way, has it been modified for some reason?
if you're having trouble, you might want to consider buying a larger external battery sled that holdc c or d batts and solder on the plug for the dc power in. beneficial for festivals.
jr