This is a bit of a carry-over from my other IIe card post. I picked up a IIe card from eBay several months back. It was listed as working. I installed it in my Mystic Color Classic, and while the card was recognized and I can boot the IIe, no matter what I tried, I could not get it to run the software off a disk, virtual or real. When I tried to boot to a ProDOS disk image, I get an error saying it cannot boot ProDOS.

I recently fixed up another persons IIe card and installed it in an Performa 405 (LCII) that I had to make troubleshooting easier. After I repaired the card, I was able to get it to boot from my external drive with an Oregon Trail disk. I was also able to get it to boot from my FloppyEmu. However, with no other changes, if I swap in my card, it fails to load the software. It seems to be failing to load ProDOS and I'm stuck at a BASIC command line. I was able to get it to run a simple BASIC loop, so I assume the CPU is working at least a little.

Is it possible that the problem has to do with the disk handling? Is there a chip on the card I could look at or replace with a modern equivalent? Any help would be appreciated, especially while I still have the working card at my workbench to possibly be able to compare any passive components.

Thanks for any guidance you can provide!