Here's an interesting question that I've yet to bring up ...
... I have a handful of Famicom games, most, if not all of them are HK pirates.
Some of them won't boot at all on some (of the many) Famiclone systems that I have, while they boot and play on other Famiclones BUT cause wicked on-screen distortion that looks like some type of power "leak" causing the television screen to "warp" or "roll" as well as producing audible "buzzing" ... and those SAME carts work completely fine on OTHER clones in my collection.
What on a cartridge would cause a system to do that? Are we looking at a potential short on the cartridge ... or a resistor or capacitor that's wired for some other overseas standard?
Or is it just the product of sub-standard parts that were used in these things that some clone systems tolerate and others don't?