This as a very early Rev 1 Apple II. It’s my main Apple II machine and i’m trying to find out why it works fine 90% of the time, while the other 10% it crashes and hangs or just displays odd behavior. Until I figure out these issues I have swapped out the motherboard for another later Rev 1 motherboard that works flawlessly.

My setup with the original motherboard is as follows:

0 - Ram card
1 - CFFA #2 (prodos 1.1.1 / contiki)
2 - SSC
3 - empty
4 - Uthernet
5 - Echo 2
6 - Floppy I/O
7 - CFFA #1 (turnkey startup to DOSmaster 1.7)

I have tried the system with minimal cards and it still exhibits weirdness. The symptoms are:

• Sometimes hangs on boot.
• Strange inverted period often seen in top left corner when booting from CFFA #1
• Sometimes crashes to the monitor

1. •Doing a IN#1 to launch the CFFA #2 always hangs with a strange flashing inverted period in the top left corner. often with corrupted type on the prodos launch screen.
   

2. •Once it’s up and running it's usually fairly stable unless I reboot.
   

3. •Have run a looping game for many hours with no problem, but crashed to monitor as soon as I restart.
   

What I have done:

• Tried a new set of ROMs
• Run Apple test utils on the RAM and ROM...no problems found.
• Run the machine from a known good IIe power supply.

Fix #1 -  I/O select chip 74LS138 @ H12
This fixed the problem with not being able to access the slots correctly. However it seems I haven't fixed all the issues yet. There seems to be a heat related, or possibly a cold solder issue somewhere. These kinds of problems are notorious for being difficult to resolve. Upon restart (after the machine has been off for some time), the computer will crash into monitor right after displaying the 'APPLE ][' text. Successive restarts seems to allow the boot process to get a little further. If I leave the machine on for a minute or so, the next reboot will work fine and from that point on the machine seems fairly stable.

To be continued...

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