gkmaia Posted January 7 Report Share Posted January 7 (edited) I got this error 00000003 00040000 By looking at Troubleshooting_Your_Macintosh_1992 : The RAM test failed while testing bank B, after passing the chunk tested for code $0002. The Z field indicates which bits failed as in code $0002. Also the second line shows what bits may have failed. But not sure how read 00040000 and what clue it makes. I was initially running 4x256kb of RAM I am sure works. Also tried to eliminate bank B by switching the resistor from 35 to 36 and using 2x1MB. Still the same issue. Edited January 7 by gkmaia Quote Link to post Share on other sites
SuperSVGA Posted January 7 Report Share Posted January 7 I think it's saying that it thinks bit 18 is bad, although I may have my math wrong. Theoretically setting R36 and putting the SIMMs in bank A (slots furthest from the edge of the board) seems like it should have worked, so I have a feeling someone else is going wrong. Quote Link to post Share on other sites
gkmaia Posted January 7 Author Report Share Posted January 7 Yes, that is weird. I removed U12F and 11F as I am getting D9 in the data bus stuck high when compared to a working board. As they were the buffers between processor and memory I thought they could be stuck open. But they are both fine. Also the ROM ICs use the data array but I tested them on another working board. Problem is this schematic is quite incomplete... the other weird thing is that Sim 1 bank A and sim 3 bank B use the same buffer. Same for sim 2 and 4. This means this type of fault should be on the sim card, not on the main board. So... confusing... not sure. Quote Link to post Share on other sites
gkmaia Posted January 7 Author Report Share Posted January 7 WOW spot on! A block of the LS257 failed open, exactly where the bus signal was stuck high. Replaced it and booted just fine! Quote Link to post Share on other sites
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