Found it
Notes:
- A500 schematics really needed
- rev6a pin out
- chips must be fast, ALS, F or AS.
- may not work with original A501 because it has extra buffers that can delay signals too much. (most/all 3rd party expansions don't have buffers)
- cut all connections in JP3, RAC0 = topleft, RAF0 = bottomright
- don't forget +5v and GND connections
- J7A = original position
- JP2 = 1MB chip position, A23 = original position
(I built this ages ago and it did work, but also sold the Amiga with expansion ages ago..)