Oct 042016
 

Got this Golden Axe 2 rom board (here plugged on a working Sega System 32 mother board from an Arabian Fight) with a black screen on boot:

goldenaxe2-1

I borrowed a friend’s working Golden Axe 2 rom board for tests and found out that the security board was the faulty part:

goldenaxe2-2

This board uses an encrypted V60 CPU to prevent conversions by swapping ROMs between boards. For example, there is the exact same board on Arabian Fight but CPUs have different IDs:
– 315-5533-01 for Arabian Fight
– 315-5533-02 for Golden Axe 2

So obviously, putting the security board from Arabian Fight didn’t make the game working, even with the EPROM from Golden Axe 2 plugged in.

ROM, PAL, oscillator and 75HC04AP were tested good but I found a few address lines which looked inactive with the scope. So the faulty chip could be either the CPU @U2 or the RAM @U1. As the encrypted CPU cannot be retrieved anywhere else than another Golden Axe 2, replacing the RAM was my only chance to repair it.

The RAM is a Fujitsu MB8421 (16 kb CMOS).

goldenaxe2-3

I bought a new one (got a MB8421-90L instead of the original MB8421-12L but not a problem as it is a faster 90 ns instead of the original 120 ns), replaced it and luckily the game booted with no other issue. đŸ™‚

goldenaxe2-4