RE: More Omega Race notes

Well, I hae spent more time in the shop on this one omega race board. Still not working.
 
I did find a problem in the vector generator counters. One of the '670 was outting out a weak signal, and the counters were not counting right. This got ridd of the scrolling vectors, but now I have good garbage on the screen.
Decided to go back to basics, and plug in the 9010a to re-test ram etc. All ram showed good, the 5101 always shows bad in this board...this might be a clue for later on.
 
The vector roms are fine, food checksums (fluke-sums, that is) 8086 (funny huh?) The main program roms are suposed to check to DEC1 (oh, my, just decomissioned a VAX at work), but they don't. Crap. Kown good roms.
 
Check J, okay
Check K, okay
Check L, okay
Check M, crap. It's a new checksums every time I do a rom check.
 
I pull the 5101, all the other roms, and all ram. Buss should be clean. Checksum it again (4 time) and a different checksum every time.
 
Pull the chip (actually I tried 3 of the same chips, 1 from a know working board) and put the L chip in the M spot. Check out fine. Put the M chip in the L spot, still, multiple checksums.
 
So I check the power situation, and discover there may be issues. I cannot get up to 5 volts. Fine with my 2 working boardests, but this one is dragging power down to 4.7. Don't know how I'm gonna track that down.
 
Arghh....
 
Mike

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Received on Thu Dec 4 22:36:36 2008