Exciting! New! Pac-Man Plus
Pac-Man Plus was a 1982 upgrade kit for the original Pac-Man arcade game. A lot of machines got converted back in the day, but ultimately Ms. Pac-Man proved to be more popular.
The game is basically Pac-Man with a few graphics changes, and some random events designed to make the game harder, and to frustrate patterns.
What made Pac-Man Plus so hard is the fact that it features all the difficulty of Pac-Man, without the patterns that made Pac-Man playable. You might say "I don't use patterns", but everyone does in some way, even if they are unintentional. Ms. Pac-Man also got rid of the patterns, but Ms. Pac-Man is a much easier game than Pac-Man, which is one reason why it got so popular. There actually are some patterns to Pac-Man Plus, which I will touch on a little bit later.
In Pac-Man plus you simply cannot count on anything. You can't even be sure that you are going to get that brief bit of safety after eating a power pellet. If you go into with you usual Pac-Man opening moves then you are going to die in seconds (it seems like all the popular normal Pac-Man patterns result in instant death on Plus, which was probably done purposely).
But don't think for a minute that this is a game that cannot be mastered. It can be. There are even patterns that you can exploit. You can develop patterns (through trial and error) for each level, which will work until you eat either a power pill or a bonus "fruit". After that you are going to be on your own due to the randomizing effect that those items have. With a bit of practice you will probably be able to get to the point where you can at least make it through 7 or 8 screens (which is about as far as I can get). After a bit of practice I got better at Pac-Man Plus than I am at BurgerTime (now that is a hard game).
Collectors Information
When a collector finds a Pac-Man Plus machine, he will almost invariably turn it back into a normal Pac-Man. If a collector finds a Pac-Man Plus PCB it will almost invariably be turned into a Ms. Pac-Man PCB (they tend to do the same thing with normal Pac-Man PCBs also). Chances are very slim that you will actually encounter a Pac-Man Plus machine anywhere. I have been active in the online arcade community for some time, and there are only a handful of guys who actually have Pac-Man Plus machines. Now the Pac-Man Plus marquees and daughterboards are very common and nearly worthless. If you own a Pac-Man then you might want to consider picking up a Pac-Man Plus daughterboard off eBay so you can switch back and forth between the different versions fairly easily.