Issue on my Bally 'Little Joe'
When the 10-points relay is energised (by hand or at the playing field) a spark is seen between the switch ground-white/orange.
At the image you can see the switch. I've looked at the schema and the switch (with wire color W(hite)O(range) schema switch 57) is doing something with the 00-90 step up relay. I cannot figure out what exactly. Maybe someone can tell me.

When I disable this switch, by sliding a small piece of paper between the switch leafs (see attached image), the machine is working normally. All 4 players can play, the score's (10, 1000 and 1000's) for each player are added correctly ands the score reels are turning smoothly.

Now I'm confused, because although I'm blocking "a function" with a piece of paper, the pinball is running like it should.
Maybe someone can help me out on this matter.
Many thanks in advance and merry christmas!

Additional issue: Suddenly the head of my pinball remains in the dark, no active lightbulbs? any idea where to start looking (fuses are ok, pinball is running)

LJ-10pointsrelay (resized).png

I did check the resistance and it turns out that the coil of the 00-90 step up unit has a resistance of 0.4 ohm, so nearly to zero and the cause for the short circuit. It was the cause of the problem. After I decoupled the coil of the 00-90 step up unit from the circuit, no short-circuit spark is seen at the 10-points relay.
Also the machine doesn't kills itself anymore and the 10-points are added nicely to the score reels.
Thank so much dr_nybble and pinhead52 for helping me out on this matter. I will order a new coil to replace the damaged one. Thanks again!

Thanks for your reply @currieddog, I have checked the Locked relay switches and the fuses/ It turms out that one of the fuses made no connection with the fuseholder. After cleaning and tightening the fuseholder, the backbox was full of light! Thanks again man!