Check and clean the leaf switch for game start it's probably dirty and needs a good cleaning, mine did the same thing awhile back. I used a thin piece of cardboard and cleaned the contacts so they were nice and shiny then adjusted, no more two player accidental starts.

sorry for the 4 year old necro-bumpage here

but from reading thru the RPG postings this problem is related to the green label game code - i am having this same issue also with a Blackout and it is definitely not the switch #03 start leaf switch since i have verified it will do this when the switch 2J2 & 2J3 harnesses are un-plugged and a jumper is used to activate the switch matrix # 03 thru the pins on the board, it still will start a two player game with a single touch and if you do touch the pin two times it will sometimes start a 4 player game

i can see how if the machine was not in free play this may not even be noticeable but when credits are abundant it is a problem because you can only start a 1 player game about 50% of the time - the other 50% are 2 player starts

has anyone found a cure or reason why some machines do this and not others?

Just yesterday I started up a Gorgar that has been in storage for 25+ years. It is doing the same thing but with so many other minor issues to fix I haven't looked into it yet. I was guessing dirty switch. I'll know more by end of day but I do know that none of my Williams "green label" games exhibit this behavior.

My Firepower does it occasionally also. Figure I need to adjust the switch gap, just too lazy. Maybe it's more than that?

am thinking that if i take it out of free-play with zero credits add a leaf switch under the existing credit / start switch and use that to add credits maybe i can force it to start single player games

but i should probably pull the existing roms and verify the check sums first maybe there is an error

I don't remember the thread, but I thought there was one here where someone found replacing a capacitor took care of the problem. If someone has plenty of time to read through all the Blackout posts, they may find that one.

am going to check the board mounted pull up resistors, caps & voltages for both lines later this week when i get back to this machine

will also try to locate the thread/posts you speak of ...

I cleaned and adjusted the credit switch on the Gorgar I'm working on that had the same issue and all is well. One player per push.

Watching and added to favs. My flash had never done this until the other night. Lots of 2 player starts. Yeah it's a system 6 mpu with green flipper roms.

stopped by today and replaced all missing grounding screws from all backbox mounted pcbs, inspected and tested continuity of the ground plug - OK there, then replaced the diode on the eject hole coil

so far i have started 5 single player games in a row with out a problem - not a large enough sample to say it is fixed so will keep testing / playing

btw, i had already replaced the credit switch diode, cleaned & adjusted its leaf switch and inspected the harness for shorts .. oh, and repaired some wiring hacks done to the coin door

Clean and adjust the gap on the start button. Make the gap fairly tight like 1/16 to 1/8 inch. I find if the gap is too wide, it doesn't make solid contact and the CPU can read it as multiple presses. I've had this on several system 6 games and each time it was due to the leafs making contact just as the button was pressed in almost all the way.

decided to replace diode on the eject hole switch and check its gap as well, have gone from very rarely starting a single player game to now starting a two player game with only one push of the credit button maybe 1 out of 20-25 or so games

since it still occasionally does this i haven't found all of the culprits - yet, never give up never surrender

ok so now the jury has reached a decision .... game was used in the tourney at SFGE this year and did not have a single 2 player start so we can call it fixed / repaired

parts used: 3 diodes, several screws for the pcb mounting plate