6821 PIA

6821 integrated circuit, PIA - "peripheral interface adapter".  These are used in pinball machines going all the way back to 1978.  Very common failure, especially if there was an over-voltage problem.

Datasheet

Bally E-620-29, E-00630-0029

Williams 5A-8972, 5430-08972-00

All tested good on a Bally MPU board. See the pics below.