So I decided that without a working set of a Defender boards it was going to be impossible to progress the machine further, as not having any control test for the boards we have meant that guess work and luck was about the best we could hope for.

So I got in touch with a legendary Williams arcade expert in the UK and sent off a combination of CPU boards, ROM boards and some sound boards to try and up with a set that worked.

A few weeks later and after some very informative chats over email (more notes to follow) the boards arrived back and it was our job to plug them and try and power up the machine.

First run, and nothing 🙁

It turns out that actually the wiring harness has a slightly dodgy connection to the CPU board so I metered all of that until it was correct and finally the machine powered up 🙂

As the video below shows initially we were getting, life but no clear picture but still progress.


It turns out that Defender output NEGATIVE synchronisation signals for its monitor whereas our Wells G monitor was looking for POSITIVE sync signals

A few changes around of the connections and we have this – a working Defender (separate post about synchronisation signals to follow!) :-))

Defender - Working