[sdiy] Lifespan of Electrolytics?

[harry]

Right... The temperatures are usually specified at 85C or 105C for high
temp
units.

How do they get this hot ???  AC Ripple current heats the caps due to
ESR.
Except in switching power supplies, welders. etc... you will never go
there.

BTW higher voltage units at the same capacitance USUALLY has higher
ripple
current capacity...and bigger cans are better at getting rid of the
heat.

For those you just MUST use big caps... these days there are film
capacitors
that offer excellent performance. They are very big.  One 1400uF / 900V
cap
that I use has the same ripple current capacity as 6600uF electrolytics
(four cans).

Just what you need for the ultimate tube amp filter cap.  I also have
some 2800uF /
900V caps at 300A ripple current. Woah !!!   If the cops pull the plug
on your gig
you could finish the night on the stored charge...

H^) harry

Steve Ridley wrote:

>  > What is the expected lifespan of electrolytics, Officially, as low
> as 1000 - 2000 hours for some types.!  Pause while thatsinks in.  40
> days continuous.  That's from manufacturers spec.  But that'sa worst
> case, plus some pessimism thrown in to cover themselves. In practice,
> things aren't as bad as the spec suggests.  These figures willat
> maximum temperature etc, and the initial deterioration may be very
> minor.The lifespan is largely determined by how the cap is used. > and
> what are the effects of old and ageing ones? The first signs of ageing
> I know of are that the effective series resistance(ESR) starts to
> rise.  A new electrolytic will typically have an ESR in therange 0.3
> to 2 ohms.  As the cap deteriorates, it can increase tohundreds of
> ohms.  This isn't a big issue in most audio applications, butin
> switched mode PSUs, TVs/monitors and anything that has to run athigh
> frequencies or deal with spikes etc, it can be a problem.  I'd
> expectESR problems after 5 - 10 years, but have occasionally had
> troubleafter as little as three years. My PC PSU died recently.  Only
> five years old and only used for anhour or two per day.  Bad
> electrolytic.  Capacitance still measures OK,but ESR around 15 ohm
> instead of 0.5.  It was right next to a heatsink,so it got nicely
> cooked.  This is fairly common in my experience.Replace them with
> higher temperature ones if you can - they'll lastlonger.  85 deg C
> caps are the norm, but 105 deg C ones aren't muchmore expensive and
> should last longer. Capacitance won't change very much at first, so a
> cap that is acomplete dud in an SMPSU may have little or no effect at
> audiofrequencies.  I work with broadcast mixing desks which are
> usuallypowered all the time.  The inside temperatures are often hot
> enoughthat you can still just touch them without pain.  In those
> circumstances,caps start to show significant serious of capacitance
> after 10 - 15 years,producing bass loss and phase shifts. > Is it
> worth the trouble going through any old gear including synths that
> are> past, say, about twenty years and giving them a electrolytic
> overhaul? Unless there are hot spots or reasons for the caps to fail
> prematurely, thenif one cap is bad, then the rest won't be too healthy
> either.  Caps are cheap.If you have time, I'd suggest replacing
> them. > I just purchased a kit (of course) of an ESR meter that
> supposedly will find faulty caps> due to their high ESR reading.
> Anyone here have experience with it? I use a Dick Smith ESR meter at
> work.  If you have to fix switched mode PSUs,monitors etc, it's worth
> it's weight in gold.  You can test the caps in circuit too.You need to
> know what value to expect, and having to look up the values isa pain,
> but it's the only way and the tester has a look-up table on the
> front.It cost around £70 UK, so I guess that's around $100.  Ours get
> a lot of use.There are a couple of other makes of ESR meter.  I have
> no experience ofthem, but there are reviews of them on the internet.
> Look for the Satcurewebsite... Does that help?   Steve Ridley

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