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