Re: [gentoo-user] Re: [O/T] PSU caps

[Dale]

Michael wrote:
> 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.
>

It also has a indicator that tells when it is done protecting or
something happens and it trips the breaker. 

>> 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.
>

These also have a indicator that indicates when they have absorbed all
the surges they can.  In the past, I've had a few go out.  I replace
them when needed.  The biggest issue with power around here, sags or
just total blinks.  Our power company has surge arrestors in several
places along the lines.  Sometimes when I'm driving down the road, I see
them.  They place different kinds of protection devices to help protect
from different power issues.  Some are just a basic spark gap that when
the voltage gets to high it sparks and some are large cans which work
like a large MOV.  Very effective given the high voltages on the wires. 
Sometimes after a large storm comes through, I see them in the bucket
trucks replacing them.  No telling how many TVs or deep freezers that
may have saved. 


>> 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).


They may be OK at the moment but what about a month down the road?  Six
months down the road?  Yea, the one with the most pressure, read that as
heat, voltage and other conditions, may pop first but the others may
follow suite sometime after that.  The thing is ten years old and the
other caps are likely the same age.  Of course, power supplies nowadays
have really good protection.  Odds are it won't do any damage outside
the power supply itself but there is always a risk.  Given the price of
a decent power supply, it may be better to just buy a new one.  It is
tempting tho. 

Dale

:-)  :-)