In part 1 I discussed the varistor and how it protects your game from power surges (over voltage), which is an external fault. Fuses protect your game from excessive current (amps) draw which is an internal fault. Fuses are rated in amps, even though they also have a voltage rating. When replacing fuses it’s important to never exceed the rated value or to bypass it. Fuses are an intended weak point.
Excessive current draw is usually due to a short, power going to ground where it isn’t supposed to. It can also be caused by overloading a circuit. Unlike voltage, which is electrical pressure, amps are the amount of electricity. It is the amount of electrons flowing through the circuit.
1 amp is equal to 6,241,510,000,000,000,000 electrons flowing through a conductor per second. You can research this further if you’re interested in getting into the physics of it.
One thing to note about amps is only the amount needed is drawn. For example, taking the 6 volt bulb analogy from part 1, let’s just say for simplicity sake that the bulb draws 1 amp of current. If you connect that 6 volt bulb to a 6 volt power supply that can deliver 15 amps the bulb will burn happily all day long.
No matter how many amps the power supply is capable of delivering, only the 1 amp needed will be drawn. Now if you connect 20 6 volt bulbs to that same 15 amp power supply, the current draw will overload the circuit and will either blow the fuse (if fused properly) or will cause the power supply to shut down.
The fuse rating should be high enough to allow the circuit to function but low enough to blow as fast as possible to prevent damage to wiring and components or even worse a fire. The more electrons that flow through a circuit, the more heat you get.
Excess current through underrated components causes them to overheat and burn. Think G.I. connectors. That’s why when converting your games to LEDs you will forever prevent those connectors from burning up. LEDs draw less current than incandescent bulbs. That’s why I also recommended in a previous PRO TIP to use lower rated fuses. A 2 to a 2.5amp fuse in place of a 5amp should do the trick. Try a 2, if it blows go to a 2.5.
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Frank
Thanks for the write up. Can you explain the advice that one can use a higher voltage fuse without problem (but as you explain above, not a higher amperage fuse).
You’re welcome, glad to be able to help you have a deeper understanding of how your games work. The fuse voltage is a safety rating. Any voltage can be used on the fuse as long as the working voltage does not exceed the fuse’s voltage rating. This is similar to capacitors. You can use a capacitor with a higher voltage rating than what is specified. I think it would only become an issue if you’re using fuses that are designed to work at much higher voltages as in the thousands and tens of thousands of voltage. Since the fuses in typical pinball machines and arcade video games are in the 250v range it won’t be an issue.