chris Unknown

Looks like it's reading corrupt data from the main ROM. Don't touch U1331 (boot ROM) since it seems fine. While it is possible for the main ROM bank (U800-U803, type 28F080 I believe) to go bad, I would first suspect PCB damage from the original capacitors. This is well documented and must be addressed before any further troubleshooting.

The old forum is still up: https://forum.tek.com/

That doesn't appear to be the case anymore, it redirects to this new forum now ?

Agreed. Please keep it somewhere as a read-only archive, there is a lot of knowledge in those old threads.