> From: Chris Zach > The MSV11-QC board ... failed startup diagnostics with what looks like > a stuck bit. .. now I need engineering schematics for that board so I > can replace one of the 41256 memory chips. On the positive side it looks like > a pretty obvious stuck bit, just need to know which chip is at that > address and memory location....
I suspect you're out of luck on the prints, I think all there is is the User Manual. Not to worry, it should be pretty easy to create a bit->chip table, I did that for the MSV11-J: https://gunkies.org/wiki/MSV11-J_QBUS_memory#Technical_information when I needed to repair one; it should be pretty easy to duplicate the process for the -Q. I did it with a 2-instruction scope loop, doing a word write to a given location, floating a '1' bit along a word of '0's, looking at the 'data in' pin on the DRAM chips. I see the -Q has a 17x8 array of DRAMs, so 16 bits of data and a parity bit (odd chip out); so in some ways even easier than the -J (which had ECC). 8 banks, but with a little luck they're in some sort of logical order. I have a -QA, of the later etch rev, which is the same etch as your -QC; so I can help with the mapping process, if you need it; let me know. Noel