One of the members of UKVAC (Aaron) put together a piece of test gear that allows you to visually check the signals on an IC whilst the board is running normally and I picked one up earlier this year as it can do a few things that the ABI Board master cannot.
Having sourced a good variety of test clips I used it in anger for the first time today.
I had a Sega / Gremlin Vic Dual PCB that should run Carnival, however it was quite dead just showing some light blue bars on the screen. (so some things were running – important for Slice, it needs to see activity on the ICs to be able to tell you if it is performing correctly)
I used it to trace back from the /WRITE signal to the ram chips to see where it went astray. (n.b. Slice cannot check three rail ram chips, but then neither can the ABI)
As can be seen from the above snip from the Slice program, it is indicating that Q3 and /Q3 are in error 5% of the time, but more importantly – they never change. (ignore pin 2, it has been disabled since I could not get a good contact to it with the test probe)
Replacing this chip gave the more usual screen output.