I've checked into it.

I traced it back to the CPU board, it's labeled "IR DET M+ (SERV/CHG) S" on the schematic. The plug is a live input to the CPU and I'm assuming it is for an input device mounted in the place of the SERV/CHG switch. Sending pulses from the plug to the CPU did nothing.

Pitts256, I’m surprised you got nothing from sending the pulses. The only thing I can think of is you didn’t have the correct chip in place when you did the test?

According to member ersk3 at the time of his post (March 09, 2017) either chip SP585 or SP1168 were the only chips he was aware of that would accept the 50ms pulses that convert to credits.

Now it seems as of (2021) ersk3 has listed these chips:  SP585, SP618, SP655, SP667, SP674, SP714, SP 742, SP765, SP876, SP1041, SP1138 & SP1168 as being compatible to work with the 50ms pulses.  These chips are found in the list here, you will however have to download the list: https://newlifegames.com/nlg/index.php?topic=33460.msg177252#msg177252.

ONLY the chips identified with (Yes) in column “NRI coin acceptor according to PSR” are the likely candidates that will work. Notice that SP585/SP1168 are among the list & are the ones that ersk3 experimented with and were found to work. NOTE that SP1137 (Montana chip) is not listed.

I’m guessing your test was conducted with the SP1137 chip as this would be a logical choice not knowing about the SP chips for external coin acceptor (NRI) that administrator knagl mentioned here: https://newlifegames.com/nlg/index.php?topic=15051.msg80738#msg80738

How are the pulses to be delivered to the purple & green wire, not sure I understand exactly how this should be done? Maybe you could elaborate?

I just got this running and have a very minor problem that I was wondering if you could help me with. The black above the numbers and letters towards the top of the CRT is a bit off, the payout number is also not centered vertically in the black. I tried the pots on the monitor and centered it nicely on the screen but it just moves the whole screen with these. I think it might be convergence issues?

This is from the how to post for s2000.
You may want to look there for other helpful hints
https://newlifegames.com/nlg/index.php?topic=327.0

David Walz,

 Attached is a photo of the proper 25¢ coin head.  The ones with spikes are guides to align the top door and coin mech on slant top machines.  The dollars coin head enters on the left side as the coin comparitors are installed in a reverse position.
 

Thanks, can you point out what components are involved ?