I have both an HP 10529a and a BugTrap 20 pin version. I've not found them to be consistent but I'm guessing it's me and not the tools. They sure seem simple enough. But then I saw this post from Brian B, posted years ago, that gave some good insight. Especially point #3.
I'm sharing to bring the topic back to the top but also to see if there are other tips out there.
@brzezicki said:
For what it's worth I've found mine to be very reliable HOWEVER
1) the chips must be super clean, clean with a wire brush even if they look good. otherwise your output is going to be a mess
2) sometimes will give false positives (that is the chips say they are bad but are not), I think I've had two or three false negatives, but not many at all that I can recall.
3) remember you won't be able to use these to identify the chip thats bad on a shared bus since multiple chips could be creating the problem.
4) if the chips outputs are pulled high or low on the game PCB, then they will show as bad.
when they are probably not.
but the big thing is #1 which creates #2
you must clean the chip first then if it still shows bad, just gently rock the clip back and forth on the chip to make sure it is getting good contact. That and always trust your judgement, if you think a chip is bad but it says it's good pull it anyway or test with another method such as a o scope or logic analyser.