Try re-seating the connectors on the MPU. You obviously have a connector problem, not sure why the lamp driver showed it, unless you bumped one of the connectors for something else fiddling with those ones.

How can this be a connector issue? The setting of the number of balls is simply set by the dip switch setting (switches 31 and 32) on the MPU. To me it would seem that the overall connections between switches 31 and 32 and the other relevant areas on the MPU is the issue.

Any chance of swapping the MPU with a known working one?

Bally's will do all sorts of weird things when they have bad connections, it's like only some of the signals get sent and returned, just like if a dip is set to the wrong setting.

So, is it just the speech calls are incorrect? Or is the game actually on 2 or 4 ball as well?

Actually I experienced a similar issue where the machine was set to 3 ball and at start up it would occasionally say "4-ball". It seemed that the issue was the connector on the solenoid driver board (top right board and top right connector).

Note that we have a new alltek MPU board, and that by wiggling the solenoid driver board connector, the call out discrepancy would revert back to 3-ball. Perhaps it is a bad solder joint there or a bad connector. I redid both.

Either way, please report back your findings and solution.

I would check the RAM chips on the MPU (probably the 5101.) The dip switches are read by the software at boot and stored in RAM, which is why changing dip switch settings after power up requires a reboot for them to take effect.

Some games use the last few audit settings to adjust # of balls. If so, make sure you batteries are good and the audits are not getting scrambled.

If # of balls is set via dip switches, check the dip bank for proper operation. Sometimes they get dirty and never close.

I am trying to understand how this can even happen. On my Embryon I have not seen any way to set things to anything other than 3 or 5 balls. Someone used a marker on the apron insert to indicate 4 balls which I thought was weird.

I initially thought the setting was 3 or 5 ball, and once stored in RAM the memory could be corrupt and change the value. But after reading the manual, I see the number of balls can be 2,3,4 or 5. It's set with dip switches 31 and 32. As Andrew stated, switches can get dirty or affected by battery corrosion and not function properly. Flush them with contact cleaner and see if that helps.

Embryon manual balls per game.png

Both 32, 31 are set to OFF for 3 ball. For the MPU to misread 4 or 2 ball, one or both dips have to start conducting (ON, ON or ON, OFF). Try cleaning that area really well. Make sure something is not on the board conducting around those DIPS. A bunch of diodes feed those DIPs too. Maybe one of those is failing.

Use your meter on resistance to check the dip switches. Make sure they close all the way and no resistance.

Resistance across the diode installed in the board won't tell us too much. Those diodes are fine unless they got phyiscally broken. I have done hundreds of these MPUs and never had to mess with those banks of diodes.

More likely to have an issue in the dip switch itself. Those are often flakey. Specially the ones that rock on the pivot point in the middle. The switch ones are more reliable.

check tp5 for +5vdc. check tp2 for +12vdc. Check everywhere you touched your soldering iron too.

You probably have a small solder bridge, it happened to me once. I could not see it at all, just swiped the hot iron between several sets of pins, tried it again and it was all good.

Best case fix is to replace the socket. That requires practice and good tools.

If you want to try and cheat. Use a machine pin socket and stack it on top of the failing socket The legs are little fatter and may buy you some time.

Nice find! Did it fix the original problem too (X no. Balls at start)?

Did you ever try swapping the RAM chips, starting with the 5101?

Yes the dip switches are read and stored in RAM. Can't tell you if it's the 5101 or 6810, but we all know which one is more likely to be bad.

21 and 22 should not be tied together. Pin 22 is 5V power and pin 21 is address line 4.

Don't really have any suggestions other than to ask if that socket was ever replaced. The solder pad could be gone on the top side as well as the through hole.

Wish I would have paid more attention to your first post. Do you have pics of your right flipper switch config?