This 50% active cycle TTL clock generates signals from 4 to 20 Hz. Its power must be supplied with 5 V and other frequencies can be generated with capacitor replacement.
This tester from a 1960 magazine is only for capacitors with insulation voltages above 200 V (110...
Epcos TDK TB2569 Film Capacitor EPCOS / TDK offers through Mouser Electronics are line of film...
This power supply can be implemented with a TIP32 providing an adjustable output at the 2k2...