From owner-freebsd-smp Wed Jan 29 18:46:32 2003 Delivered-To: freebsd-smp@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 60EE737B401 for ; Wed, 29 Jan 2003 18:46:30 -0800 (PST) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id B2C8A43F3F for ; Wed, 29 Jan 2003 18:46:29 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.12.6/8.12.6) with ESMTP id h0U2kT0i084871; Wed, 29 Jan 2003 18:46:29 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.12.6/8.12.6/Submit) id h0U2kTbJ084870; Wed, 29 Jan 2003 18:46:29 -0800 (PST) Date: Wed, 29 Jan 2003 18:46:29 -0800 (PST) From: Matthew Dillon Message-Id: <200301300246.h0U2kTbJ084870@apollo.backplane.com> To: Peter Wemm Cc: Dale Woolridge , freebsd-smp@FreeBSD.ORG Subject: Re: Over heating of the ABit BP6 motherboard References: <20030130022752.1872F2A89E@canning.wemm.org> Sender: owner-freebsd-smp@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org :The voltage spikes are the kicker, aren't they? In my research for the :dead Apple Airport problem (caps swelling up), somebody reported that the :spikes he was seeing were way above the nominal rating of the capacitor. :Although the input is 12V, and the caps were rated at 16V, he ended up using :25V caps because of the spikes. I did the same on mine. : :I suspect I have the same problem on my 8 port switches at home. Two of :the three have now had an exploded electrolytic capacitor and subsequently :shorted out the external power wall transformer and killed it. Collecting :up the bits of the capacitor and replacing it solved the problem, but :I'm not sure if I want to keep losing the power supplies. : :Cheers, :-Peter :-- :Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com :"All of this is for nothing if we don't go to the stars" - JMS/B5 It's most likely that the capacitors are simply being made from substandard materials with higher internal resistances. Sometimes you can get around that by specifying HF (high frequency) caps. Voltage spikes above the capacitor's rating (or even just near the capacitor's rating) tend to blow holes in the gap material, greatly reducing their life span, but won't necessarily make them melt down. e.g. a capacitor spec'd at the voltage it runs at might last 20 years. A capacitor spec'd at twice the voltage it runs at might last 40 years. Anything that blows out in less then 10 years is more likely to be workmanship/materials problem (unless it is consistently overvoltaged). The electrolyte dries out too quickly and/or inherently high internal resistances cause overheating in high frequency applications (such as switching power supplies). The manufacturer might have put in non-HF caps when he should have put in HF caps, etc. The sad thing is that most brick makers don't care. If the brick lasts 5 years they are happy campers. This is why a 20 year old T.V. might still work while a 10 year old computer might not. My old Amiga still works but I've had plenty of computers bought since then fail for all sorts of reasons. Substandard materials. Ah well. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message