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)
![](https://macros-arcade.com/wp-content/uploads/2023/09/74LS175.png)
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.
![](https://macros-arcade.com/wp-content/uploads/2023/09/IMG_20230928_204352-728x1024.jpg)