I was donated some non-working main boards from the old William's game Defender.  Including several ROM sets.  The biggest issues is the connectors for the insertable Ram/Rom chips are old and will not maintain good contacts.  My project is to build an authentic Defender standup game, using old parts from various non-working Defender games.  I have main boards, rom boards, wiring harness, coin door, and a control panel from original Defender machines.  I will need to cut wood to build a cabinet, but getting a working set of electronics is part of may standup defender project for 2021.