Sometimes when troubleshooting circuits, I will check a cap using my meter and it appears that it is working (even out of circuit). Although when I find that all other components are good, I will replace that capacitor in question and WALA!! the device now works. What is up with that? I check them out of circuit with an ohm meter, watch the deflection, switch leads and watch the deflection that way. I even check them with a capacitance meter to see if they read the proper value and they will. I'm not saying this always happens, sometimes I find a shorted cap or one that is open. Is there a sure fire method of testing these rascals? Another question: To power l.e.d.'s with 120vac, you need a cap in the circuit. I am told that they have to be non polarized, but all the non polarized caps I ever see are only up to 50 volts. Where can I find a 150 volt one or is there another way?