I don't know whether you've been following the controversy with Dell computer, but it involved exactly this issue (though not with power supply caps). They had this issue with motherboard capacitors that were defective and exhibited this failure mode. It was not because the capacitors were subjected to overvoltage but rather because they were mis-manufactured. One batch of Dell servers experienced a 97% failure rate. Dell has taken some heat on this because they went to some lengths to disavow the problem and occasionally blamed the customers for the issue. If I remember correctly, the capacitor manufacturer in question was Nichicon. John Hansen On Wed, Jul 14, 2010 at 10:27 AM, Roger Weichert wrote: > Hi guys, > > I've been going to ask for a while about possible causes for the failure of > some 10,000uF 35v electros that are used in a basic power supply for a > pulsation controller. > > There are 7 of them in parallel and on a couple of occasions I have seen > where nearly all have swollen and split their tops and leaked and dried > out. > In fact they rattle quite noticeably when you shake them. > > >From my understanding I thought that electros only burst if they are fed > with AC or if their voltage rating is exceeded. > > In both cases the rectifiers were ok and on fitting new caps the supplies > worked fine. > > The originals are rated at 35 volts and even unloaded have a maximum of 15 > volts applied. The 240v input would have to more than double to get the > secondries anywhere near 35v !!! > > The originals were also only rated at 85 degrees, and I've fitted 105 > degree > replacements, but while excessive temperature can dry them out, I wouldn't > have thought it would cause this problem. > > I've uploaded an image at http://imagebin.ca/view/HX_1Ati.html > > Any thoughts please. > > Regards, Roger > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist