Got this Taito Megablast for a repair:
When I powered it up, I was greeted by a solid black screen, /RESET and /HALT on main 68000 CPU were stuck high.A visual inspection revealed that JAMMA connector was oxidized.Once cleaned it, the board booted:
As you can see both tiles and sprites had sever issues, besided the sound was all garbled and scratchy:
So, for first I went to dump the devices containing tiles/sprites (three 40 pin MASK ROMs 27C400 compatible) and audio samples (two 32 pin MASK ROMs 27C040 compatible) and dumps were not matching the MAME ROM set for the ones @IC32 (sprite data), IC58 (tiles data) and IC29-IC30 (audio samples data) :
Loading my dumps in MAME I could reproduce the issues more or less accurately:
Replacing these bad MASK ROMs with the equivalent EPROMs fixed completely the game.