Here is some info I discovered a few months back when I was considering the purchase of a Superman with the same problem. Seems like it's a common problem. It comes from this website:

http://www.pinwiki.com/wiki/index.php?title=Atari_Repair

If you get yours fixed please let me know as I'm still considering the purchase. Good Luck!!

Pertains to Atari Superman and Hercules pinball (Atari Gen2 Circuit Boards)

If all playfield coils except for the flippers do not work, the likely suspect would be the chip enable circuit that is based around the CDN4013 chip located at B4/5, and also utilizes the MPS-A06 transistors at Q65, Q66, Q81, Q106 and the SJU783 transitor at Q103.

Other than the chip-enable circuitry, the solenoid driver section on the Gen2 Atari driver board is a very simple circuit layout. A single MC14514B line decoder controls each of the individual solenoid circuits. Each solenoid circuit consists of only an MPS-A06 pre-driver transistor, which drives the SJE783 driver transistor.

There is some confusion regarding driver transistors, as the schematic lists the driver transistor to be an SJE783, while the board layout lists a 2N6041, but most boards used an RCA8203B. The SJE783 is essentially impossible to find any information about, and the RCA8203B has been unavailable for quite some time. While the 2N6041 is available, a cheaper and more robust alternative would be the TIP107. Note that this applies only to Superman and Hercules boards, earlier machines used different components.

The MPS-A06 is still a commonly available part through most large electronics houses.