Tell a -35/-133 MPU from a -17 by counting J5 pins

Besides the silkscreened number, connector J5 identifies the board: 33 positions (counting the empty key) on an AS-2518-35 or -133, and 32 positions on an AS-2518-17 (page 6). A -133 is simply a -35 with R113 replaced by diode CR52.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35

Related tips

• Telling a -133 MPU from a -35 or -17
• Converting a -133 MPU to a -35
• -17, -35 and -133 MPU boards compared
• Telling a -17 MPU from a -35 by connector J5
• Convert a -133 MPU to a -35
• Power and ground pins of the main MPU chips
• Jumpers for a -35/-133 MPU running two 2732 EPROMs (U2 and U6)
• What changed on the -133 MPU: zero-cross sensing from 6.3 V AC

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)