On Wednesday, 28 October 2020 22:57:25 GMT Dale wrote: > Michael wrote: > > On Wednesday, 28 October 2020 19:27:06 GMT Dale wrote: > >> I'm thinking about replacing that cap and seeing if it works. I've > >> repaired a few monitors that way but my question is, should I trust it > >> after replacing that cap even if it works?? Should it be load tested or > >> something? Does the protection circuitry only work once? > > > > It depends what was damaged and the cause of it. It could be the > > capacitor > > reached its predicted end of life. It could have been a transient > > voltage, in which case more things in the protection circuit (diodes, > > resistors) may have also been damaged. > > > > I had an old desktop which during a lightning storm ended up with a blown > > PSU and a blown winmodem. The winmodem was unrepairable, but the PSU > > survived following the replacement of a single capacitor. :-) > > > > For the cost of a capacitor I'd give it a try and then measure the output > > voltages under load. > > Well, we getting rain but I haven't heard a single bit of thunder or any > light blinking. Nothing really bad anywhere near us either. It's the > hurricane thing again. I might add, I got surge protection coming out > my ears. One in the main breaker box that should protect everything. > It's installed right below the main breaker.
This type of surge protectors are good for mains transients and can be reset when they trip. > Another one at the wall plug where I plug my UPS in. These may or may not reset - depending on the type. The multi-socket extensions with varistors (MOV) in them are not a fit and forget item. If they have seen repeated or prolonged overvoltage conditions close or above to their clamping voltage value, they can and do degrade over time. So you may think I'm well protected me, but when the next transient comes along the surge protector provides next to no protection at all. A close by lightning strike will cause the varistor to fail catastrophically, in which case you'll know it's cooked and take action to replace the unit, but otherwise you wouldn't be aware of its suboptimal capability. > End of life. That is my bet. I did a search for when I ordered the > power supply. It is within a month or so of being 10 years old. I may > replace that capacitor just for giggles but honestly, I got my money out > of that thing a few years ago. I'd be worried about the other > capacitors in there too. Are they about to pop as well?? Who knows. If they are not domed they ought to be OK. A big power surge will overheat the capacitor, causing the electrolyte paste to evaporate fast and blow its top off. Lower surges, or operating in overheated conditions for prolonged periods will cause it to dome as it expands. It may also cause it to leak slowly, in which case it may not pop/explode. There are a number of failure modes of electrolytic capacitors, but I don't recall all of them. The wear and tear of capacitors is a function of temperature and voltage. As long as both are kept low they will last long(er).
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