Power supplies with solid polymer caps
in [Repair]
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From: William Sommerwerck on 20 Nov 2009 22:13 >> It's true that electrolytics are among the least reliable of components -- >> but they're not /that/ unreliable. > Yeah, they are. I've personally changed a couple thousand - 10x more > than all other components combined - even mechanical wear out parts. Yes, but you're a service technician. I'm talking as an owner.
From: William Sommerwerck on 20 Nov 2009 22:14 > Depending on how stressful the position that they are used in - and many > such positions these days *are* - I would have to beg to differ. They really > are /that/ unreliable ... If that's the case... then why have I had such good luck? I just remembered another failure -- bypass caps in the video driver board of my NAD.
From: stratus46 on 21 Nov 2009 00:05 On Nov 20, 7:13 pm, "William Sommerwerck" <grizzledgee...(a)comcast.net> wrote: > >> It's true that electrolytics are among the least reliable of > components -- > >> but they're not /that/ unreliable. > > Yeah, they are. I've personally changed a couple thousand - 10x more > > than all other components combined - even mechanical wear out parts. > > Yes, but you're a service technician. I'm talking as an owner. I also replaced a raft of them in some of my personal gear. The WORST 'lytic caps are the surface mount units which fail early and often. Panasonic FK series are certainly better than OEM parts. G²
From: Jeff Liebermann on 21 Nov 2009 00:29 On Thu, 19 Nov 2009 21:44:36 -0800, Daniel Prince <neutrino1(a)ca.rr.com> wrote: >I have read that electrolytic capacitors are the least reliable >component in power supplies. Not exactly. The problem seems to be a mixture of counterfeit electrolyte in some low-ESR electrolytics, manufacturers using electrolytics that are operating far too close to their rated working voltage, and too high a working temperature. Lifetime on electrolytics is predictable and calculatable: <http://www.edn.com/article/CA6588368.html> <http://www.illinoiscapacitor.com/techcenter/lifecalculators.asp> <http://powerelectronics.com/mag/power_optimize_electrolytic_capacitor/> If you plug the operating temperature, working voltage, etc of your favorite motherboard or power supply into the formula, you'll find fairly short predicted lifetimes. Note that the operating temperature is NOT the ambient or case temp. When you shove a bunch of ripple current through a capacitor, it will get hot from the internal resistance. Measure the temperature with an IR optical thermometer for a better value. The counterfeit electrolyte problem is probably what you're seeing on motherboards. The crud is still in the system even 10 years after the initial introduction. Some history: <http://en.wikipedia.org/wiki/Bad_capacitors> <http://www.badcaps.net/pages.php?vid=4> >I have also read that there are >motherboards with solid polymer capacitors. Sure. However, they're very difficult to identify without back tracking the part number or chopping one in half and looking for the black goo inside. The clue is that they tend to be short and not very tall, while conventional electrolytics are much taller: <http://www.niccomp.com/NIC1202_InFocus.pdf> <http://www.mec-italy.it/pdf/nic/nspzr.pdf> The caps in the photo really are solid polymer caps. <http://www.capacitorsplus.com/whatis.htm> >Are there any power >supplies with solid polymer capacitors? Dunno and too lazy to tear apart a PS and check. >Thank you in advance for >all replies. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com jeffl(a)cruzio.com # http://www.LearnByDestroying.com AE6KS
From: Jeff Liebermann on 21 Nov 2009 00:33
On Fri, 20 Nov 2009 21:29:31 -0800, Jeff Liebermann <jeffl(a)cruzio.com> wrote: >The caps in the photo really are solid polymer caps. ><http://www.capacitorsplus.com/whatis.htm> Oops, wrong URL. See: <http://www.dslreports.com/forum/r19863881-Solid-Polymer-Capacitor-Failure> -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com jeffl(a)cruzio.com # http://www.LearnByDestroying.com AE6KS |