Aug 012010
 

Received an “untested” Bomb Jack board from eBay.
It appears to be a bootleg/original hybrid. The A board was a bootleg, the one with only 2 x AY-3-8910’s on it and the B board is from an original.

The game was missing the green and blue colours and sound was stuck in a constant repeating loop from power up.
The RGB, sync and video ground go to a 5 pin header on this bootleg, not a 6 pin header, the previous owner was clearly not had an adapter or plug for anything on this board and had soldered the wires directly on, had also melted all the plastic supporting these 5 pins so a couple were shorting to ground, easy fix. The sound had a corrupt EPROM, I erased and burnt a new one, still no change. The RAM had already been socketed so I tested it and it came up clear. Checked the Z80 with the logic probe and found the address lines were all high except for a couple that were pulsing. De-soldered it and tested it, it failed on pretty much everything, replaced it and now the sound was working but seemed to be lagging behind when compared to MAME. I put in a new RAM and the fault was fixed. Swapped the RAM back and fault returned. This RAM works fine in my other boards so am putting it down to RAM speed.