Sounds more like the master than the connectors. I don't think the exact same problem would follow the displays if it was one bad connector. Here is a picture of how Williams doubles wires in Molex. They clipped the wire and put them together. Not sure about Flash Gordon though.

image (resized).jpeg

If it is the connector that will super cheap.

I just rebuild a bunch of bally displays. Reflow the solder on the header will help sometimes, redoing the connectors is another one that helps, especially if its following another known good display. I had to replace the chips on a few to fix weird issues. But if you do that, socket them for future ease.

Put the suspect display in another slot that is working fine. That will tell you if it's the display or the connectors.

Those pins aren't really designed to accommodate two wires, especially the insulation. I have found stripping and crimping like the illustration to work well.

pinning 2 wires .156 (resized).png

Don't overlook the display data connectors on the MPU J1.

Oh, and yes just snip the wires off the old connector and double them up in a properly sized molex. It's quite easy if you have the right tool.

This is what I would do.

Power up the game and GENTLY flex MPU J1's wires (not the housing) while watching the displays (you always carry a mirror, right?) to see if that changes the displays any. If yes, repin and reflow or replace [edit] *MPU* headers.

CAUTION! HIGH VOLTAGE PRESENT ON DISPLAYS!

If no, power down and disconnect all 5 displays. If P2 slot is not the goofy one, use it as a test bed. If it is goofy use P4.[edit] *P2 and P4 are most accessible and convenient for swapping*. Connect each display to the test harness and start display test from the coin door. Make sure all segments, all digits cycle through correctly. Disconnect and repeat with the other displays, noting any weak or otherwise bleary segments. If all displays are found good, pick the brightest, clearest one and try it at P1-P4, running display tests.

From your description one position should be goofy with all displays testing good. Except Credit/B.I.P, just leave that one disconnected.

So then you can try repining the connector. As suggested above reflow solder under ALL headers, ALL displays. They are ALWAYS cracked on either end up to 4 or 5 pins, so just do them all.

[edit] *When you reinstall displays, put the 'freshest' one in P1, next best in P2, etc. If they all look great, good for you! The last thing to do is to adjust the HV down a few volts so the displays don't run as "hot" and maybe extend their life a little.*

IMO!

Yeah, it's the only way to make it really dependable. Those springy connector pins aint so springy no more.