PCB 
My Apple II Motherboard

 The PCB is an old replacement.  It differs from the original in that it contains the color killer and I believe, the 6 color change that Apple started shipping at around serial number 6000.   When it failed while in use by a business, the original was replaced by a computer shop.  I'm on the lookout for an older one without the color killer mod.  This one works, most of the time, but it is not entirely reliable.  This is mostly due to bad connections between the ICs and the sockets.  In my opinion, Apple didn't use the best sockets in the world on these machines.  This picture show some tarnish on one of the IC's pins, which is also part of reliability issue.  I may go through the machine and clean up each pin on each IC at some point.

Update on the PCB

After being frustrated by intermittent operation for some time, I went ahead and cleaned the pins on every chip on the board.  I very carefully used a polishing bit at slow speed on a Dremel type tool on the removed chips.   After completing the job, it appears that the reliability that one should expect from a Apple II. has returned to my machine.

Color Issues

I usually have this machine connected to a monochrome monitor.  While experimenting with another machine that had horizontal sync lock problems, I discovered that the color feature of this machine wasn't working.  After debugging for a while, I decided that the master crystal was out of tolerance and wasn't generating a good color reference frequency in the video signal.  Sure enough, I swapped in a crystal from another board and suddenly the missing color appeared.

Update 5/27/2007 More Instability

Well this motherboard has given more more trouble.  See my Apple II repair page for a description of couple of IC failures that I had to fix.  Since then, operation has mostly been good, with a bit of intermittent operation, due to bad socket connections.  This appears to be in the video generation section.  For now it hasn't been frequent enough for me to bother to debug.  Trying a contact cleaner, such as Deoxit or Stabilant 22, may be an alternate worth pursuing in the future, since the mechanical cleaning was only partialy successful.

Since real rev 0 motherboards are so expensive, I'm working on a project to build a clone Rev 0 motherboard board.  See my recreation pages for news and updates on that project.


Back to Mike's Hobby Home Page