Hi Klokkie
I agree with wizardblom - the bakelite spacers in a switch can shrink and the screws may get loose --- a good article to read is the whole "2f.": http://www.pinrepair.com/em/index2.htm#clean .
In post-10 You write "Extra-Step on Coin-Unit" - followed by "(so goes to player 2)". I have a problem in understanding - to me "going to player-2" means: The Williams-Player-Unit is stepped so player-2 plays the ball and makes points - faulty as the game has been started as a Single-Player-Game.
"mysterious-fault-A" - do You have an unwanted step on the Coin-Unit (Backglass shows "Two can Play") - or is it a "One can play game" but faulty player-2 gets the points of the first kicked-out ball ? When You start a new game (so You start a One-Player-Game) - and the mysterious-fault-A does not happen - You then press for "Two can play" - do You ever have faults showing up ?

Please do a test - play a ONE-Player-Game till Game-Over so the Score-Drums of Player-2, -3, -4 are all resetted / they all show Zero. Manually step on the Score-Drums of Player-1 - put exactly 00400 points on the Score-Drums of Player-1. Then start a new game - question: Does mysterious-fault-A happen ? (((see the schematics at "7-E" - I have the wacky theory: The Make-and-Brake-Switch on Score-Motor-Index-Wheel, Switch-D, the outmost blade does not touch the second blade when the motor is running. With this switch "Index-D" faulty: The pulling Reset-Relay quits pulling too early. Well, a theory is a theory - I assume You have faulty stepping on Coin-Unit))) Greetings Rolf

Hi Klokkie
toward the end of my post-12 I asked You to do a test --- what is the reaction of the pin ? When You do the test 2,3,4,5 times - do You always get the same reaction of the pin ? Greetings Rolf

Hi Klokkie
I hope for luck - as the result of Your test supports my theory --- please do the same test - this time putting manually exactly 00800 to the Score-Drums - and the pins reaction ? Greetings Rolf

Hi Klokkie
I forgot to ask You to also do a test with exactly 00500 Points on the Score-Drums. Greetings Rolf

Hi Klokkie
just play a game till Game-Over - have the Score-Drums of player-2 and player-3 and player-4 all on Zero --- manually set the Score-Drums of player-1 to (00400) - do a test /// set to 00500 - do a test /// set to 00800 - do a test.
The theory I am after is: Having the drums to 00500 then do a start needs FIVE pulses from the turning Score-Motor to step the drum forward to Zero. Having the drums to 00400 then do a start needs SIX pulses from the turning Score-Motor. In ONE turn of 180 degrees the motor can fire maximum FIVE pulses --- doing the test 00400 therefore needs TWO turns of 180 degrees. When the Reset-Relay faulty drops out too early then the Coin-Unit can get an pulse to step-up.
This is my last post for today - time to go to sleep, till tomorrow, greetings Rolf

Hi Klokkie
thanks for doing the tests --- I am surprised / perplex. At the moment I do not have an idea - lets both of us look at the JPB - "what happens in a functioning Jackpot" - We start a new game - ... Coin-Relay pulls in and establishes Self-Hold-Circuitry, the pulling Coin-Relay closes switch "my red 1" and closes switch "my 2" - the motor (my 3) starts to run. The Game-Over-Relay is tripped, switch "my 4" is closed - the Reset-Relay (my 5) pulls in and establishes Self-Hold-Circuitry "my 6,7,8" --- the running motor actuates "my A1 and B1" five times in a turn of 180 degrees - the pulsing relays (my A2, B2) make the Score-Drums to reset. The Coin-Relay is pulling and the Reset-Relay is pulling and the motor is turning - through "my 1, 8, 10" the Coin-Unit-Reset (my 11) fires.
Towards the end of the turn of 180 degrees the "my brown star" Switch in SCM-5A opens, Coin-Relay quits pulling and so switch "my 1" opens. The Score-Drums may need more pulses to completely reset - the pulling Reset-Relay through "my red star" make the motor to do another turn of 180 degrees - nothing can happen as switch "my 1" is open.

My theory was "the motor makes another turn, the Coin-Relay is faulty still pulling, the Reset-Relay faulty drops out too early due to faulty "my 8" open switch --- through "my 1, 9" and the switch on the no longer pulling reset-Relay (my blue star): The Coin-Unit faulty steps up.

Klokkie - do You have some 24VAC Test-Lights we can hook-up as shown in the lower right corner of the JPG - then taking the Test-Light near the Score-Motor and look at "exactly what moment in the turn of the motor does the Coin-Unit faulty step up". Greetings Rolf

0Jackpot-Work-01 (resized).jpg

Hi Hans
I do not want to destroy Your happiness (partially fixing a fault) - when You adjust the switch (my red 9) too much so it is faulty ALWAYS open: The fault "faulty stepping-up the Coin-Unit" does not show up - but other stuff now does not functions. See to the right of "my red 9": The Replay-Unit-Reset-Coil must fire (taking away a replay from the Replay-Counter) - does this functions after You have adjusted "my red 9" switch ?
You and I we live in the same time-zone - for me it is late, I go to sleep. Till tomorrow, greetings Rolf

Hi Hans
we press the Replay-Button to "NG - start a new game for one player with all the resetting stuff" --- or to "AP - add a second or third or forth player to the game".
The beginning of "NG" and "AP" is the same - see the JPG - The Reset-Relay does not pull (does it pull in YOUR pin ?) so switch "my red 1" is closed, the motor is not running so "my 2" is closed, we close the Replay-Button (my 3), there are Credits on the Replay-Counter so "my 4" is closed, when at least one of the switches "5,6,7,8 is closed: The "9" fires and through "10" the "11" is activated --- the "9" and the "11" have Self-Hold-Current, stay pulling until in the end of the one turn of 180 degrees the motor-switch "13" cuts the Self-Hold-Circuitry and the "9" and the "11" quit pulling. You always can cheat a bit - forcing - You manually actuate the armature on "9" or on "11" - BUT: Wear rubber gloves for insulation as 24VAC can kill people.

The "5 6 7 8": When the game before has ended normal (reaching Game-Over): The "6" is closed. As all the balls have been played in the game before: The "7" is closed. Has the game before been a ONE-Player-Game: The "8" is open - has the game before been a 2,3,4 -Player-Game: The "8" is closed. Has the game before been a 1,2,3 -Player game: The "5" is closed - has the game before been a 4-Player game: The "5" is open. We can cheat, force - we manually activate the ("9") Replay-Relay and the Coin-Relay must pull-in and the motor must run and the Replay-Relay and the Coin-Relay must stay pulling for the one turn of 180 degrees of the Score-Motor.
Attention: When we do an "NG" - during start-up / resetting: The "5" is made closed as the Coin-Unit is made to reset, the "6 7 8" are made open.

Try this manually activating - write about - we then will have another look at the JPG in post-29. Greetings Rolf

0Jackpot-Work-02 (resized).jpg