I recently discovered a rework defect in an Amiga 3000 daughter board; a similar defect might affect other Amiga 3000 systems out there. The fault causes corruption of Zorro III transfers. The daughter board in question is Rev 3.0, which is the oldest shipping revision. This might be a one-off board defect. I wasn't able to find photos of the bottom side of any other Rev 3.0 A3000 daughter boards to help confirm this.
The daughter board has two extra wires added as part of what I assume was factory rework. These connect:
RP603-5 and CN603-51; this is Zorro _CINT, a.k.a. _EDS0.
RP608-2 and CN602-98; this shorts Zorro ED(5) with _SCS a.k.a. _EDS1.
The second rework causes a short because the schematic shows Zorro pin 98 already connects to RP608-5, and Zorro pin 86 already connects to RP608-2. This results in Zorro pin 86 getting shorted with Zorro pin 98 on the particular Rev 3.0 daughter board that I have.
I put together a video which summarizes the debug process I took to discover and fix this issue. It's available here:
https://youtu.be/BPxm2OTUIuQFollowing the fix, I was able to use both an X-Surf-100 and a BigRamPlus in the Amiga. Both were previously not functional in this computer.
