Is there any possibility the eprom chips are installed "off" by one or more pin holes of the socket?

nope double checked and rechecked. I have tried 2 different brds. Thanks for the quick reply Vic

What does the service tool say? Can you communicate w/ the service tool?

sure sounds like software is corrupt or power supply is still bad, no ac riding on the 5 volt power supply, should be less then 10 mv ac, did you install the new software on the original board? if so maybe the board corrupted the software at that time and is the reason it would not function on a new board. is 12 volt power supply good? if you had another car to experiment with, try moving your software from vertex to a good car. I am not sure, would have to check, but isn't M0 a RAM chip, are you moving it along with the eproms that go in M1, M2 etc. maybe the Ram chip is bad. did vertex send you a chip that would go in the m0 slot, the older boards had a removable m0 chip, that had a tag like the eproms on top of it, the newer boards have m0 soldered in place and hence non removable.

found the problem. Oddly enough one of the chips from vertex came with the sticker on backwards so, we did not know it was in the socket backwards till we pulled it of to check it. It read good but, did not have the same check sum that vertex did. Replaced it all is better now. I want to thank all you guys for the help. Chuck

Whew!

never look at the sticker, always look at the little notch at one end of the eprom. top left pin next to notch is pin 1 when checking eproms, the checksum is the most important thing that must match the old eprom

chuck thats a good get. i remember a new lift co trying to do the right thing by copying chips in a newly acquired 401's and put them in the wrong and kaboom. gained the job friday lost the job monday!

Came in with a hangover one morning 30 some odd years ago and put in all 14 of them in backwards.. 😁

ouch