I am struggling to get a Williams Sys 3 Disco Fever running. The machine has been dead for over 20 years and there were a lot of parts missing off all the boards including the ROMs.
I have repaired a number of Williams 3-6 boards over the years but this one Is bugging me and it seems to be rom based.
If I run the Leon’s rom in U17 everything works, I can do a full test including driver board outputs ( after repair), however if I install all Disco Fever ROMs the board will not boot, it locks up with two solid LEDs. I believe there is an issue with ROMs, there is a thread talking about the World Cup prototype/production rom. Currently the machine runs partly, it has the U14 and U20 ROMs for Disco Fever but will not run with U17, burnt twice and checksum ok. If I run it with the World Cup U17 rom I can get the machine into diagnostics but all the switch assignments are wrong.
Can anyone shed any light on this weirdness ?
Are the Disco Fever ROMs ok?

Thanks,
These ROMs came from Ipdb and second time from planetary. I am a member of vpforums so will download theirs.
As an aside, I was hoping you would answer this, I think you did the last thread

If I run a set of Flash ROMs, I never have a boot issue, everything just seems to work

I will try U17 from ipdb again.
Pinwiki has a reference regarding the World Cup white flipper rom U17 works in all other white rom machines. This is my current configuration but it seems to be quite random as to whether it works or not.