While I'm still developing my ideal pinball troubleshooting board for your Williams system 3 through 7 pinball machines, I have come up with an intermediate solution for those who need to get their machines up and running today.
It's called the Pincoder Adapter, it comes preloaded with the Pincoder diagnostic software, and is ready to go out of the box. You do not need a chip programmer or any chips to use it.
You can find out more and also purchase the adapter here:
Of course, if you have questions you can certainly ask them here and I'll be happy to answer.
Thanks and happy repairs!