Hi
Don't have that pin. but would suspect a switch adjusted too close.
does that pin have a 100K relay? or a bonus relay?
do all the step units advance correctly? disk contacts line up correctly on every step up/down?

Hi mrbanjo
You have an Interlock-type relay for every player. These relays ca be "mechanically faulty" - question: Does the fault on player-2 ONLY happens when PLAYER-2 is playing ? (Same: player-4 ?)
The fault randomly occurs - question (on player-4): The player-4 may have 12580 or 17430 or or or - he also can have 9780, 19360, 29780, 39240, 49730, 59180, 69460, 79770, 89930, 99180 - question: is it true randomly --- or does the fault ONLY happen when the 1000 to 9000 Score-Drum of player-4 has "9" visible ? (((See my examples .9..., 19..., 29..., 39... etc.)))

I assume "only when 19..., 29... etc." - I made a snippet of schematics from ipdb-schematics. I believe the "encircled rosa / pink" switches do operate correct. "encircled green" most likely operates correct - it is the switch that says: "Me, the relay HAS tripped - I will stay TRIPPED for the rest of the game - NO NEED to send another shot of electricity to trip me --- as I AM TRIPPED".
So the "encircled red" Switch is in question - (((the "encircled orange, fourth player 1000 - 9000 Score-Drum-Switch '9th position' " is ENTITLED to be closed whenever player-4 sees the "9" on the 1000 - 9000 score-drum))) - THE "fourth player 10'000 - 90'000 Score-Drum-Switch '9th position' " is ONLY ENTITLED to be closed in position 90'000 to 99'990' - when the player-4 sees the "9" on the 10'000 - 90'000 score-drum.
On player-4 the "switch to look at the score-drum 10'000 to 90'000" has wires soldered-on: Red-Green, White-Brown. Nice, You should see, follow wire White-Brown leading over to the Score-Drum 1000 to 9000 of player-4.

I can read Bally-Schematics --- I have never worked on a Bally pin --- I hope another pinsider participates and tells us about "how do 'position-9 switches' look like on a Bally pin".
Great - player-1 has no fault - may want to investigate FIRST on the functioning Score-Drum of player-1 (((see wires White-Green, Green ? on the score-drum, in my JPG))), - study the stepping, switches beeing moved - THEN look at score-drum of player-4 (and player-2). Greetings Rolf

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