Weird thing started happening on my Black Knight LE, I figure its a chip or something, though I've never messed around with those.

It won't remember high scores after you turn it off and worst of all it displays all 4s as 0s and 5s as 3s, so you never know what your score really is. Anyone else ever have this issue? I don't know how old the batteries are, but the guy I bought it from said they were pretty new (five months ago).

Remembering the highscores can be the battery, or the circuit it is feeding (wires, corrosion, 5101 IC, etc)

Is that the only mis-interpretation? If 4s are shown as 0s, there is a binary coded signal coming from the CPU to the master display board, but that would mean signal C1 (as shown in the schematics of the master display board, left side) is missing. If that is so, it would also mean 7s show as 3, 6s as 2s and 5s as 1s.
Is this applicable for all displays? That is also strange since players 1/2 are different from 3/4.
Can you check all the connectors of the master display board, and 1J5 of the CPU? And reseat them?
Can you disconnect all displays from the master display board, and connect just player 1, and do the same for player 2,3,4?
Does that make a difference?

Just got back from vacation, thanks again to everyone for their help.

Yes - very new to taking care of my own pins. This is on location, I've fixed a few things since I bought it, this is the last and it'll be good to go.

I'll check the batteries, hopefully that kills the high score problem.

You were right, it isn't the only misinterpretation. 7s don't show up at all, I guess I just didn't see it. It is applicable for all displays.

The master display board is mounted right behind the backglass bulbs, correct? And the CPU is top left inside?

Here are pictures of both. I don't know where C1 can be found, exactly (googled my butt off for schematics, foudn some for $45) but I did find an empty slot on the top left of the CPU board (or what I think is the CPU board). Check it out, is that 1J5?

Also missing are two of the six rectangle shaped chips in the middle.

Also, on the left side of the supposed CPU board are two red rows of switches, all are set to on except for both 7s. Just noticed this, could it make a difference?

0704131443a.jpg 0704131443.jpg

OK, found a system 7 schematic PDF, found 1J5, its definitely plugged in all the way. I'm going to try reseating very carefully.

Also, ran the diagnostic while in there and #9 comes up, which says MEMORY CIRCUIT - could this be the high score circuit? If so, do you know where that is?

Reseating all connectors to the display board didn't help, I also reseated 1J5, everything looks good in there too, no luck.

Nevermind, the coin door was closed *slaps forehead*