Problem

Bad sprites:

Diagnosis

There appeared to be a sprite ROM addressing issue (all the sprites were displaying the woman in the cutscene’s graphics data). The first place to look was the sprite ROMs:

The address registers 11H and 11J were my first suspicion. I couldn’t probe them directly because they’re under the sub-board but I could at least access the address pins of the ROMs. Sure enough, the output signals of 11H were very weak:

A new 74LS377 was installed and all was well.

With the game now fixed, I turned my attention to this horrid bodge wire on the underside of the PCB:

The actual trace break was next to 11H and was easily bridged with a small amount of solder. Curiously, the break was located underneath the sub-board.

Fix

Replace 74LS377 at 11H.

Philip Bennett