Going to repair an original Apple 1 this weekend

[MicroCoreLabs]

I was invited to help debug an original Apple 1 in a few days and I thought I would see if the folks in this group would like to share some ideas. The machine is number 33.

It is stuck with the whole screened filled with the pattern "@0" and my belief is that this pattern is simply the powerup contents of the video shift registers and that somewhere in the CPU data path up to the PIA video output has an issue.

My plan is to run a range of tests and tools using my MCL65+ in place of the 6502. It can simply emulate the 6502 to see if the original ceramic 6502 is broken, can emulate the motherboard's RAM and ROM, and can perform hard read/write/dump tests which it can report to us via the USB serial interface.

I welcome any ideas or suggestions to debug this rare and historic machine.

Thanks,
-Ted

 

[skate323k137]

Ted,

If you haven't already, I would scour the AppleFritter forums. The member there, "Uncle Bernie," has spent endless time debugging the hardware and electrical engineering of the Apple 1. He even has/sells complete tested burned in IC sets (not saying to get one, just informing you, that's his level of knowledge and experience).

His document he provides with kits to build replicas with his IC sets is 70 some pages, full of advice for reliability and soldering etc. He may be willing to send you this doc.

Best of luck in your endeavor with this quirky but historic machine

Alex