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