Thursday, October 6, 2016

Fixing Apple IIs

Since getting my Apple //c in June 1984, I have been a huge fan of this machines, and I regularly browse Craigslist for machines to rescue. I now have 6 machines of various kinds in my garage, maybe it is time to admit that I have an issue.
Over the last 5 years, I managed to locally find a couple of original Apple IIs, great machines, but both were upgraded to Applesoft roms. Back in 1979, I would have done the same, upgrade to a newer firmware, get new features. I do this with my phone, my car, whatever can be upgraded.  But 30 years later I am trying to get things in their original state.
This means re-installing the original Integer roms. For many hardware fanatics, this is fairly easy, but I am not one of them :)  I had both machines open on my workbench swapping roms right and left, but could not get them to work, various errors, no boot. Removing chips from the board with a screwdriver, installing new ones, testing, back to step 1.


Browsing the 
Apple II Enthusiasts group on Facebook, I got in touch with John who lives close by. He agreed to help me, so I went to see him with my machines, and a bunch of roms to try out. This ended up being a great afternoon, I met a great guy, so knowledgeable of both hardware and software.

Opening Apple II and starting the tests

Home made board to test main logic steps

The machine would boot to a garbage screen, but never complete the process. John used his own board that checks every important chip for i/o, voltage.


Removing each chip and single testing them. Found 2 4116 ram chips in the process

Magnifying glass to look at the board and traces

After checking every chip (replacing 2), the machine is still not booting, time to dig deeper. John opened Understanding the Apple II. This book is a collector item, I had one at some point.  It was nice to see the actual value of the book at work, it is not only an expensive collector item, it is also a very useful book.


Image result for Understanding the Apple II book
Understanding the Apple II



Still not booting
Wile John was deep into following flow diagrams, I browsed his amazing colleciton. If I have a problem with 5/6 Apple IIs in my garage, he has 20, at least....


Finally the error was diagnosed, My screwdriver skills cut traces on the board. Not surprising I admit.


This means it is getting better, I learned. And it is finally booting.




My fixed Apple II running Karateka




 Rebuilding it


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