Originally Posted by
Compute
The 2600jr has a ribbon cable which connects the switches (built into the top half of the console) to the motherboard. It sounds like somebody took it apart and did not put it back together right. Try taking the cover off and see if the ribbon cable is connected. It is kind of tricky to keep it connected while putting the cover back on but it will work.
As for the cart connector, it would help to see a picture of it. The tabs and whatever SHOULD open the cart, so if there are no tabs you may need new ones. Or see if you can't find a jr that has an intact cover but is broken otherwise and go from there