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darklife 04-09-2016 02:50 PM

80s arcade gambling machine issue
Sorry no pics or model number at the moment.

I am going to be taking a look at a floor arcade machine for a friend to see if I can get it running.
I do have a background in digital electronics and know my way around the scope and such.

When turning on the machine it makes a loud musical tone that is stuck along with all random ASCII characters on the screen that flicker or stay stuck in the same pattern.

I tried resettling all the socketed chips and looked over the main board for any obvious issues and pressing the momentary toggle reset switch but even after that it still continues to be stuck in this condition when powering up.

Is there any obvious parts I should be looking to test on the board?
Just wondering what the general diagnostic overlook would be to get started on this?
There is some eprom chips that I wonder if they could go bad with age?
The biggest problem is the stupid main board is inside the same slot area as the coin mechanism and there is very little slack on the cables so testing/repairing it is going to be a PITA.
Also the board was just hanging in there by its cabling which I found odd. It seemed to be this way from the get go.

Thanks for any tips and ideas to get started :)

RetroHacker 04-09-2016 03:17 PM

Check voltages - a low or ripply 5V supply will cause most games to fail to boot.

Another very common problem among games is faulty memory chips. Without knowing what game this is, or anything about it, I can't give you any specifics, but, check to see what kind of memory it uses. Most games, with a bad memory chip, will crash and fail to boot with similar symptoms that you describe. If it uses 4116's, then carefully check the other two DC voltages - missing or incorrect +12 and -5 will cause those not to operate.

EPROM chips are probably fine - those are very stable. I'd focus your attention on the power supply and the memory.


Dude111 04-12-2016 07:03 AM

Good luck buddy :)

colorfixer 04-25-2016 04:14 AM

Maybe it has a suicide battery that contains some of the code needed to run? It's possible that they did this to prevent someone from tampering with the game.

MIPS 04-25-2016 11:16 AM

Did you ever get around to the photos or the model?

darklife 04-29-2016 10:42 AM

Alright thanks again guys. I tested the PSU and it was putting out something like 13+ volts on the 12v line and around 6+ volts on the 5v line!
There was a variable resistor inside that I simply played with and got the voltage to settle back to the 5 and 12 it should be, plugged in and... IT WORKED.
That was all it took.
BTW the CMOS battery was still good!
I got some numbers from the board but nothing special. It is just a slot/poker machine game like the Cherry Master ones I see online. I think I seen revision 2 on the board. I forgot the paper with the board numbers over at my friends but it has a Z80 CPU.
Actually kind of boring to play lol, just feed it dollars and you don't really win any real prize haha.
We have to figure out how to bypass the money feeder next so they can hit a magic button or something and play, while making random guests feed it money ;)
It surprised me that most of the circuitry, or at least the monitor was on a isolated 120 to 120v transformer on the bottom of the cabinet. Most of the wiring is really scattered and there is still a security box inside with cut wires going to a blue game like button on the back corner which I am guessing was a security reset? Bunch of odd stuff going on inside of it. I will try to get pics next time.

MIPS 04-29-2016 11:34 AM

In my Cherry Master machine if you short pin 8 on the edge connector to ground it counts for one credit.

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