Now that all work srams are fitted to their sockets its time to power on...........................🤞
Blimey what do we have here? good news is the cpu is running the program code,i am able to coin up and start the game with music+sound effects working.The game is displaying random trash tile grx with no colour and all the sprites missing.Ok now to investigate the tile grx generation circuit.The tile grx roms sit on the video pcb at location F7/H7,scoped the address and data pins and they were active apart from address pin21 which was low.Suspected it may be a tile grx ram,there 3 tile rams at location K6/J6/L6.Scoped all outputs which looked ok but on the ram at L6 showed 2 floating and 2 currupted signals.
I removed this ram and put in a new socket with new ram but this did not work so now i suspected the 4 bit buffer(ls244) at location L8,scoped the data pins and found 2 pins stuck high which was pin 19/17.
Powered on and......................................................................................................................................
Looks as though we have the tile grx back 
,but looking at the demo screen i noticed that the picture is shifted upwards and also in the maze when playing blind.Still no sprites or colour but slowly making progress to find that little bug!
To be continued.......................................................................................................................🐞
Blimey what do we have here? good news is the cpu is running the program code,i am able to coin up and start the game with music+sound effects working.The game is displaying random trash tile grx with no colour and all the sprites missing.Ok now to investigate the tile grx generation circuit.The tile grx roms sit on the video pcb at location F7/H7,scoped the address and data pins and they were active apart from address pin21 which was low.Suspected it may be a tile grx ram,there 3 tile rams at location K6/J6/L6.Scoped all outputs which looked ok but on the ram at L6 showed 2 floating and 2 currupted signals. I removed this ram and put in a new socket with new ram but this did not work so now i suspected the 4 bit buffer(ls244) at location L8,scoped the data pins and found 2 pins stuck high which was pin 19/17. Powered on and...................................................................................................................................... Looks as though we have the tile grx back ,but looking at the demo screen i noticed that the picture is shifted upwards and also in the maze when playing blind.Still no sprites or colour but slowly making progress to find that little bug!To be continued.......................................................................................................................🐞