Ideally with a logic probe.
Having said that, whenever I have had a neon problem on either CV or SW and I have eliminated all other components, 99% of the time it has been the ULN. I usually don't even bother to test the existing one just replace it with a socketed version - chances are the board has/is being shorted somewhere, that is the main reason for a failed ULN.
I was afraid you'd say that. The short, would it only be attributed to the neon circuit or any short what so ever. The latter will kill me.
