Hi everyone. I'm working on a SS Mata which was buried in a garage for 30 years. I've spent a few weeks replacing a few coils that tested bad, all fuses, and replaced the MPU with an Alltek. I also cleaned checked all connectors and reflowed some contacts. Ran through the safe powerup at http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Powering_up_the_first_time and she started up and played her tune. The MPU flashed appropriately, all voltages are good, and she'll coin up, but will not start a game. I also ran through the self tests and everything from the general illumination, to displays, and coils seem good.

This seems like a common issue with Matas from the threads I've read, and I've tried a few suggested fixes. Checked the start switch for grounding, checked the wires that run from the start switch through the roll tilt, adjusted the outhole switch, and a few other minor adjustments. Probably not relevant, but the upper right score display reads 11 after a few seconds of powering up. Thought it was just a bookkeeping reference. I'm sure it's something simple, just looking for a nudge in the right direction.

Thanks for the replies guys. Let me answer your Q's then give a quick update.
- The self test shows if buttons are stuck Zacaj, and doesn't indicate any issues, including with the start. Not sure if there's a way to test this particular pin switch by switch?
- I believe Mata only takes one ball Rockwell, someone correct me if I'm wrong.
- I cleaned the connectors a few times but it is entirely probable one or more is bad Xenon. The MPU board was laying on it's back in storage so the battery leak coated the entire board, which is why I didn't bother trying to restore and went Alltek. I have a rebuild kit coming for the rectifier board connectors (they're not bad, but I want to rebuild anyway), and could easily order a kit for the MPU connectors. That will be the next step barring other options.

Here's the update since I first posted: I have been able to start a few games. On powerup the score displays show 00, if I press start quickly I can play a game. Once "11" appears in the upper right display start will not work. If I powerup and wait a while the display will show 00 and again I can start a game. After one game the problem re-emerges and can be cleared only by restarting or running through the diagnostics to reboot, but then it's the same issue.

I think this probably supports a connector issue on the MPU like Xenon was saying. I'm going to give them another cleaning, and if that fails I'll rebuild.

That's good to know. I freely admit I restore arcade cabs, pinballs aren't my thing. They just keep falling in my lap. Knowing this I tried it and the start button does not show in the switch test. Other switches do.

Unplugging J2 & 3 didn't have an effect. I don't think the test button is stuck since it doesn't seem to cycle through test. I also tested the leads to see if it was stuck on. It just starts at 11.

Also, I cleaned the MPU connectors again and now the ball is being kicked out on powerup. I had this happen with another pin a while back and I can't remember what the culprit is. I feel like something is stuck or shorted somewhere.

EDIT: After I posted this I plugged J2 & 3 back in and the game was still playing as though they were unplugged. I unplugged power and plugged back in and now the game is playing perfectly. The start button issue has ceased. I've turned on and off and played several times now. I have no idea what changed? Loose connection?

I'm going to rebuild all the MPU connectors. Since the MPU board is a brand new Alltek, I won't be doing anything with that. For the time being it's still working perfectly, so I'll be doing mostly cosmetic work until the connector kit arrives. It seems pretty clear it was acting weird because of the MPU connections.