You need to keep in mind that most of the older pinball hardware are being run by pretty primitive computer systems. Williams system 3 through 11 were built around a pre-packaged computer architecture of the 6800 series processors. In these system there really are no high level diagnostics for a computer based system to interface with. There have been some programs written for the williams boards that can be used to test some of the components on logic side of the boards. I am thinking here specifically of the Leon test programs for checking PIAs and memory functions.

One thing about these systems: 6800 based systems have very little fault tolerances built into them, most of the time they either boot and run or they don't. Having a system that 'kinda' runs is pretty rare.

As pointed out earlier, this is why most of the time the most useful tools you have available to you are a logic probe, and multi-meter. I also keep an oscilloscope around so I can find 'floating' signals.

For testing most common output circuits, I use a lot of the test fixtures that are available from siegecraft electronics. That said, if you want to get into board repair, I don't know how much longer siegcraft will be around. The owner wants to sell the company. I also have a dedicated display because I work mostly on early Williams games. It was made from a kit produced by @DumbAss. You can find out information about that board here: https://pinside.com/pinball/forum/topic/dumbass-test-and-reproduction-pcbs

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