Wire a Neo Geo Credit Display

[fastredpacman]

I was wondering if anyone knows how to wire a neo geo coin counter display? I got one that I want to stick in my cab, but I can only get it to display a 0 for coins and I need to figure out how to make it display numbers when coins are inserted. Any help would be appreciated.
Thanks!!

[grafixmonkey]

What did this thing do?  Tell you how many credits were inserted total since the last check, or tell you how many credits had just been inserted, and were ready for play?

[fastredpacman]

Thanks for the interest it tells you how many credits had just been inserted and are ready for play.

[grafixmonkey]

hmmmm...
ok so how does it count?  Does it have a "count up" input and a "count down" input?  or does it take a numerical signal from the game board, and you'd need to hack something else to provide that signal?

It depends how accurate it has to be.  If all the games you'd use it on would be "one coin one credit" games, and it uses a "count-up count-down" system, you might be good to go...   could just hook your coin button to the "count-up" and your start button to the "count down".

If you tell me what the model numbers are on those black chips on the board, I can probably tell how it works.

[AlanS17]

I see some lettering refering to "main pcb". That's a bit discouraging.

If you're switching between games I don't see how this thing can be accurate, anyways. What if you count up and then close a game before your credits hit 0 again?

[Beley]

If yu can take some high resolution pics (or use a scanner) of both sides of the PCB i could tell you how to make the counter work, as all the chips seem to be standard TTL 74xxx's

on closer inspection it seems that the 2 top chips are 7447's (7 segment decoder/drivers) adnt eh bottom right one is a 74273(8bit register), i cant read the number of the bottom left chip though(?7474?).  But without being able to acually see which pin of which chip is is hooked to to what i cant tell you how to wire it up

[grafixmonkey]

I see some lettering refering to "main pcb". That's a bit discouraging.

If you're switching between games I don't see how this thing can be accurate, anyways. What if you count up and then close a game before your credits hit 0 again?

You'd need a 'clear' button, or you could rig your 'esc' key/button to also clear the coin counter.  The 'main pcb' thing might read a binary number from the mainboard, but it might also have been a simple way to gain access to the buttons on the panel.  

It's possible to build a circuit that uses your coin switches, start buttons, and 'esc' key to count how many credits are available.  However, in games that use 2 credits per play it would give the wrong value, and in games where no start buttons are used (such as TMNT and X-Men) or the gameplay buttons doubled as start buttons, it would also read wrong.  So, maybe it's just not a feasible thing to do for an emulator.

[fastredpacman]

Here is a quick diagram of the black chips. The way the counter originally worked was every time a quarter was inserted it would give you a credit up. And if you chose a game to play it would count down a credit. Thanks for all the interest and help.

[fastredpacman]

Here is the back of the board.

[Howard_Casto]

If you could get the board running on a simple creditup/creditdown then you could keep track.  Simply rig the credit up trip to buttons 5 and 6 and the credit down trip to the 1 2 3 and 4 buttons.  It wouldn't be super accurate but it'd at least be functional.  

[AlanS17]

If you could get the board running on a simple creditup/creditdown then you could keep track.  Simply rig the credit up trip to buttons 5 and 6 and the credit down trip to the 1 2 3 and 4 buttons.  It wouldn't be super accurate but it'd at least be functional.  

He's got to get his comments in. He thinks he's sooo smart. j/k

No it wouldn't be accurate...

[Beley]

If you can take some good pictures of both sides that clearly show the traces on the PCB, i could tell you which pins on the bottom connector you need to hook up to make it display stuff, but as others have said makeing ti acuratly show the ammount of credits you have would be the hard part.  The best way to do that in my opinion would be to complie your own version of mame the outputs the ammount of credits on the parallel port(which would be wired to your counter)

[grafixmonkey]

That board periodically reads two BCD encoded decimal numbers from the arcade board and displays them.  There isn't any counting circuitry on the board itself, it grabs the numbers from the motherboard and displays them.

So, you could reprogram MAME to periodically output the credit value on the parallel port, or you could build a custom board that counts up when you insert a coin and counts down when you push the start button.  It'd be pretty complicated to wire for something that would only show the right number of credits for a few games (mostly classics).