CPS-III simm problem

[huluhala]

I help my friends to repair two CPS-III PCB
First pcb I programmed ultra bios ,now it's no problem
The second pcb , checksum is the same as first pcb, can run the game , but the pcb can't shwo simm 5, if I want to program game with CD ROM, it shows "there is not enough memory....."

I have changed 1H~4H,5H 6H 9H, but ineffective TAT

 

[kazuo]

Since you said you already replaced all the level shifters and the bus ICs, the problem would most likely be either a bad SIMM slot (less likely IMO) or a bad trace somewhere between the slot and whatever it is connecting to.

You may want to perform a visual inspection of the SIMM slot (in case you haven't already) to rule that out, then start buzzing out the traces. I'd actually start by looking on the solder side of the board first (the bottom/underneath) and look for broken traces or missing components. Then check the top side.

Good luck!