I have spent a considerable amount of time over the last couple of months restoring a very flakey Apple II plus motherboard to something approaching reliable operation. I expect that over the next few weeks, some final testing and debugging will resolve any possible remaining issues and I will be able to declare that the system is working completely reliably.

At the start of this effort, this particular motherboard occasionally worked properly, but never would stay working for long. In the past I had worked with other early rev Apple II motherboards that had similar intermittent issues and assumed that a lot of this intermittent behavior was due to connector issues, as reseating chips usually improved or at least changed behavior.

In the past those flakey boards have ended up on my spares pile, but I was determined to get this one working properly. Though I did encounter flaky sockets, I found many chips that had bad outputs, which made me wonder how the computer worked at all. Once I started finding and replacing these bad chips, the stability of the computer improved dramatically.

I have posted a youtube video that shows how I debugged one particular bad chip.