Konami Hyper Sports arcade pcb repair #2
The game logic seemed to be running but graphics were totally corrupted. Tilemaps are usually easier to fix than sprite problems so I started there, but the relevant custom chips and RAM checked out fine. The breakthrough came when I noticed one of the RAM chips never had the write (/W) line enabled at any point. The write lines should almost always be pulsing on this game as the CPU writes tile data into RAM.
The V1DIR and V2DIR signals actually start on the top CPU board, but they travel to the bottom and are buffered by an LS241 before reaching the RAM chips. This chip was removed and tested bad before being replaced.
Which improved things somewhat – definitely recognisable now but still broken.
I kept on debugging the tilemap RAM and found a couple of data lines were always high – I knew the RAM was good so I started to search for ways in which the data could be corrupted before getting to the RAM. This traced back to the LS245 on the top CPU board that sends CPU data to the video board – it had failed on multiple lines so literally every byte the video board received was corrupt in some way. Replacing this fixed everything 100%.