On capacitors. They are specified to have a certain number of hours use at a given temperature.
High quality capacitors from the likes of Panasonic or Nichion will have figures like 2,000 hours @ 85*C. or 1,000 hours at 105*C.
Example:
http://uk.farnell.com/panasonic-ele...am102/cap-alu-elec-1000uf-100v-rad/dp/9693971
At lower temperatures they last longer, I'm not sure how linear the relationship is, but it is proportional. This is a valid argument for using an overrated power supply with will typically run cooler and thus the electrylitics will last longer.
The reason for the short life is simply that there is gel like liquid in Aluminium electrolytic capacitors. Even though the capacitor is fairly well sealed from the factory they do leak slowly overtime, the electrolytic effectively boils away until the capacitor fails, either short or open circuit, usually taking other things with it, sometimes dramatically.
Cheap capacitor are generally less well rated with lower life expectancy at a given temperature or a product might under spec the capacitors in terms of voltage or capacitor and the capacitor can self heat more and die younger.
There are new technologies that expand the life of aluminium capacitors such as "polymer" and "hybrid" capacitors.
High quality capacitors from the likes of Panasonic or Nichion will have figures like 2,000 hours @ 85*C. or 1,000 hours at 105*C.
Example:
http://uk.farnell.com/panasonic-ele...am102/cap-alu-elec-1000uf-100v-rad/dp/9693971
At lower temperatures they last longer, I'm not sure how linear the relationship is, but it is proportional. This is a valid argument for using an overrated power supply with will typically run cooler and thus the electrylitics will last longer.
The reason for the short life is simply that there is gel like liquid in Aluminium electrolytic capacitors. Even though the capacitor is fairly well sealed from the factory they do leak slowly overtime, the electrolytic effectively boils away until the capacitor fails, either short or open circuit, usually taking other things with it, sometimes dramatically.
Cheap capacitor are generally less well rated with lower life expectancy at a given temperature or a product might under spec the capacitors in terms of voltage or capacitor and the capacitor can self heat more and die younger.
There are new technologies that expand the life of aluminium capacitors such as "polymer" and "hybrid" capacitors.
I had no time to have a proper look as I had to rush off to work but I picked up a PSU from a local computer shop on the way home and fitted it before the house owner got back. Thankfully all was well.