Using an Arduino Nano plugged into J5 of the Bally AS-2518-17 MPU, I've rewritten the rules for Bally Black Jack to include the following:

* A Rolling Skill Shot
* Multiple levels of Top Lane awards
* Bonus up to 69k
* Ball Save
* Free Play mode
* Tournament Mode settable through front door switch
* Real Black Jack play (cards show on player displays, Hit with Player's stand-ups and Stand with saucer)
* Random Deck or Pre-programmed deck (to ensure fair tournament play)

The code an documentation is available here:
https://github.com/MrEkted/BallySternOS

(the PDF in the BlackJack2020 folder has all the build instructions and game instructions)

Here's a video of the game in action:

The daughter-card is built to allow dual boot (the machine can be booted to the old code or new with a switch behind the coin door). Here's a video of the dual boot:

The daughter card is easy to build (for less than $20 each). Here's a quick parts list that can build 3 boards:
Nano knockoff: https://www.amazon.com/Arduino-Board-ATmega328P-Without-Compatible/dp/B07XVYBR9Y/
Prototype board: https://www.amazon.com/Prototype-Snappable-Arduino-Electronics-Gold-Plated/dp/B081QYPHHP/
Connectors: https://www.amazon.com/Honbay-Single-Female-Connector-Arduino/dp/B06Y4S6G29/

With the addition of this switch, the machine can be booted to old or new code:
https://www.amazon.com/mxuteuk-Terminal-Position-Miniature-Dashboard/dp/B07XMH174C/

This is the same daughter card you may have already seen in my Stars2020 update.

pinkid
Send me one and I'll code it for you

I second that!
Or just loan me one for a month.
I almost got one in December, but wasn't fast enough.

Several of us have run this code on Allteks. Robotworkshop has a good point about the new bootloader.
I pushed new code up to the repo just now. It has some new features, so you probably want to grab latest from the BSOS library and the BlackJack2020 folder.
I put a line at the top of the setup() function in BlackJack2020.ino that you can uncomment to add a delay, in case that's the issue.
It looks like this:

// If using an Alltek & experiencing boot problems,
// try uncommenting the following delay:
//delay(2000);

With the Alltek, you don't need the jumper to the top leg of R134 (since it doesn't have one), but you do need to have a 34 pin header on your board to pick up the IRQ line from pin 34. Also, be sure that pin 1 of your board (on the right) aligns with pin 1 of the J5 connector on the MPU. That's probably obvious, but I've seen misalignment cause issues in other installs.

Black Jack has left me. I like that game a lot, but it was time for it to move on and make space for the next project. I made one last video of the new code (with bug fixes and new features) here:

FYI - Black Jack was written (and last updated) when I was only programming for Rev 1 & Rev 2 boards. It has not been updated to work with Rev 3 & greater.