Hi Bill, the A/C adapter on my 2600 is a small black wall wart type between and inch anda half and two inces thick and about two inces tall. The factory label reads:
ATARI
part no, C016353-101
plug in power supply for use with
model 2600 xep80 or sx212
input 120v 60Hz 9W
output 9V DC 500mA
it is a plug in class two transformer and ul listed 50j5 OEM