Good idea for the disco
Since the machine is displaying colours, it indicates the CPU, ROM, address
decoder and GFX chipset are all working.
Maybe it's having memory access problems, or problems with talking to Paula?
For a start try reseating all the socketed ICs, including all the chip and fast
memory.
The try swapping a few major components like Paula, Buster, Gary, Agnus with
your working A2000 and see if you get any further.
Failing that, it's disco time!
