GRAH1, I really would like to believe that it´s just a cap, but Slot-Tech sales speach indicates that "Full Power Boost feature enables extra power over and above tracks standard power output
". You can not achieve this just with capacitor. Other sentence that suggests existence of electronic booster is: "This feature will only work with mains transformer power supplies
". Why would filtering capacitor care which supply is feeding it? BUT if you have built-in booster circuitry it would need extra power for stepping up the voltage, thus giving extra boost and "speed increase of 3000-4000rpm depending on the type of motor used
". Also such rpm increase is impossible to achieve with plain filtering capacitor.
Okay, I may be wrong, but either the sales speach is extremely exaggerated or controller really has some sort of built-in power boost electronics.
Owners of Slot-Tech controller can confirm or decline. If you find an IC chip and an inductor next to the IC inside controller/box, that means booster circuit exists If there are no extra IC´s or prined circuit boards inside, then I´m wrong and my apologies to Slot-Tech.