You’ve repinned every connector, right?

All of these Bally pinballs of this age are suffering severe connector rot.

Yeah. He's serious. And he's correct.

Getting a machine this age reliable is taking a LOT of effort. It used to be that you could just reflow a pin here or there, fix the exact problem you are faced with and move on. In my experience, that isn't the case lately.

At the bare minimum, reflow the solder on every display at the connector. Look for anything that might need solder reflow at the glass and elsewhere.

Put all the displays back in, see if that 'fixed' it... for now.

Read the entire Pinwiki about Bally, particularly the section here:

https://pinwiki.com/wiki/index.php/Bally/Stern#The_Same_Number_is_Displayed_Multiple_Times_During_Display_Test

A problem with one display can/will affect all of them.

Consider replacing all of the original glass with LED replacements. Original glass and working display boards are becoming harder to find and more expensive every day.

I love machines this age, but in my experience lately (about the past eight or nine years), all machines this age are taking a LOT of repair and involve a lot of replacing all the pins and plugs. Anything less and you end up with a terribly unreliable machine. Personally, I'd do this for a KISS pinball of this age because it sells for a high price that justifies the repair needed, but I'm not taking on other models of Bally pinballs anymore. Too much work, not enough value when you get done.

I hope you get it fixed!

If all the displays are doing it most likely it's a problem with the common J1 connector on the MPU. If you haven't done so already, clean, reflow, and repin that connector.

https://www.ipdb.org/files/698/Bally_1979_Dolly_Parton_Installation_and_General_Game_Operating_Instructions_with_paginated_schematics.pdf

Any switch that has a switch capacitor on it (-|(- in the schematic page) should have it cut off and replaced. They are bad after 40+ years. You can cut one leg of them (they should look like little discs) to test. Undoubtedly as well some of you switch will have been abused by incorrect maintenance way back when - (operators continued to file switches into the early solid state era because 'that's what we always do to fix things' despite there being warnings to not file the gold plated switches.) If the gold plating is compromised, you have to replace the switch (or the contact, at a minimum). It will never be reliable until you do.

Finish replacing those crimp pins as well, same reason. The plating is gone and they will not be reliable, as you're seeing.

Return. Bally engineers called switch rows returns but R would be too confusing so they settled on I. Bally senior engineers were military trained and used military designations for many of their designs.