Maple Park, IL
There is only ONE issue left on this to resolve. You can scroll to the bottom of the post for a more direct approach to that if you like. So....
Finally pulled out and setup my Alien Poker. It's been in storage for about 8 years now. I loved this game when it was set up, despite it being a single ball compared to most games that were multi-ball by this time. It's a fast playing game with lots of action and a nicely setup drop target bank to aim carefully at.
I remember this was mostly working when I had it setup before, but remembered there were some random lockups and resets going on when I took it down.
In the mean time I had purchased a new back glass from PP the day those came out, a plastic set from CPR, and one of those dreaded playfield overlays because this one is completely trashed with about a 1/4 or better of the paint gone and lines everywhere.
So, here we go on trying to get this thing 100% functional!
I removed all the circuit boards. Any chips in sockets were removed. The legs were cleaned up and they were reinstalled. All of the connector pins on all of the boards were reflown and cleaned up. I did see now that there were a couple very small cold solder joints that I missed (and I should have just reflowed ALL of them years ago) when I originally had this thing setup 8 years ago and there were random lockups and resets.
New rubber kit and decent old ball (no point in a new ball until the playfield is replaced since 1/4 of all paint is gone anyway) installed back into the game.
Power supply voltages all test perfect. Power supply was recapped 8 years ago.... so..... probably OK to go for now. HV tests out great as well. No burning of displays going on here. 
Time to put the MPU in. MPU seems to boot up properly when watching the leds at power on.
Add the driver board to the mix and power up.
Game comes up in test mode. Coin door open, power off and on quickly and we are in attract mode. Nice.
Went into diagnostic test mode and the displays all test good.
Coil test is all good. I haven't installed the sound board yet though so there is no sound yet.
Lamp test mode, changed a few burnt out bulbs and there are 4 GI sockets that are bad on the back box board. All feature lights and playfield GI are good to go. New lights in the coin door as well.
Go into switch test mode. There are no switches stuck on and all switches register their proper switch number, however, and it seems random, sometimes when you hit a switch it will show that number and go back to the previous switch number that was hit right before it. I can bounce around the playfield hitting different switches and it seems to do it all over the place at random. The majority of the time it does not jump back to the previous switch, but it does randomly.
Have to look into that.
Lets play a game.
Hit the start button and a 2nd player is added automatically. That's not right.
Game does play and all switches score properly and the rules are being followed.
There is erratic behavior with the lane change switch associated with the right lower flipper. Cleaned and adjusted the switch and its working perfect now. It had been skipping super quickly between changing lanes and even skipping over one here and there because it was so fast. Now it's perfect.
The kick out holes are kicking the ball out almost before it even rests in the hole, so I adjusted the switches they land on and it's working perfectly now. There was almost no gap in the switches previously.
A little random scoring was going on, so I went through all of the switches on the play field and adjusted a handful of the stand up targets that were SUPER close. It seemed like one or 2 of the stand up switches were touching or so close that you couldn't even slide a paper between them.
Game is playing great now and scores perfect.
Everything here seems to be in order now except for one thing.
The game still randomly (it seems about every 10 games or so) adds a 2nd player automatically when starting a game. 90% of the time you start a game, it's ok. Weird.
I have since gone through 2 more times and made sure that all of the switches are gaped and nothing on the tabs or any wires and lugs are bent or touching.
I've gone through switch test mode and there are no switches stuck on. All of the switches register with there proper switch number. It seems like the random switching back to the previous switch number in switch test mode has been severely reduced from earlier, but it doesn't seem like there is any specific column or row that this is occurring on at all.
My guess is there is a failing diode somewhere on one of the switches and I need to really try to narrow down and see if it is specific to a column or row. Seems like that could really take some time to do. Ugh.
Any other suggestions?
I have since removed the original 5101 and installed NVRam as well. There was no change with the random adding of a 2nd player to start a game.
