There's a trace on the top layer running along the edge of the board that goes to pin 19 of the Mac floppy drive connector. It carries the data being written to the Mac floppy drive, and I suspect that it comes from pin 27 of the 342-0341 ROM chip. Unfortunately, I can't tell from the photo. The trace disappears from view in the area of the two ROM chips, and there is no via showing in the photo of the bottom layer, so it must connect to something on the top layer.
If anyone here has access to an A-Max cartridge, and can trace that connection, I would be most grateful. Refer to the photo below.
