I've changed all Custom Chips from a working A500 (including the ROMs), 'cause these are exactly the same. The exception was the bus controller chip.
Unfornatetly, the same behavior. I suspect this is caused by a faulty TTL or memory (onboard) chip.
The A520 don´t work either (I thonk that´s because the 22 and 23th pin of the RGB conector of the 2000 isn´t connected, by default). I used it only with a C= A1942 without the TTL adaptor. Used to work.
