If you have a solid state Bally pinball machine, then the solenoid driver board has a large 11,700 uf 20v capacitor on it. This smooths the regulated 5v line. 

These original components are now 40 years old, and should be replaced, especially if you are having problems.

Here we have a nice 15,000 uf 25v capacitor.   Slightly bigger capacitance is recommended and smooths better without stressing the rectifier circuit.  25v uprated from 20v.

Nice size, to easily replace the existing large blue capacitor.

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