I have a 30 yr old factory made strobe light that use to work good. It plugs into 120 VAC and has a knob to adjust flash speed from about 2 flashes per second to about 1 flash every 15 seconds. These days it flashes only when it feels like it just have to watch and wait it may take 2 minutes or 15 minutes to flash then maybe it will flash again 10 seconds later. I have tested all the parts on the circuit board and the variable resistor too they all test good. Even though parts test good I replaced the electrolytic capacitors and that has not fixed the problem. It has an small hand wound looking auto transformer I want to call a jewel thief circuit this is probably the trigger for the flash tube. Last but not least is the flash tube it is strange that it flashes at such crazy random times. It is a U shape flash tube 3/16" diameter and about 2" long if the U could be straightened out.