One of the products we service was having frequent cap failures in the switching supply, the manufacturer was replacing the caps over and over, and we were doing so as well (just to avoid the shipping for warranty repair, and to provide faster service for our customers) After seeing a large number of such failures, I hooked the scope across the caps that were failing and found they had a short duration high voltage spike across them under normal operating conditions. I soldered a small low ESR cap across them on the underside of the board and the spikes went away. One by one we have replaced the cap pairs and added the low ESR caps, have not seen one blow since. We reported the mod to the manufacturer, but they can not seem to understand how a small cap can help a large cap, but they tried it and found we knew what we were talking about. Been about a year now without a power supply going down. KF4HAZ - Lonnie ----- From: "PicDude" On the subject of DC-DC converters, remember I had a capacitor go poof on a > DC-DC converter board? I'd like to happily report that many weeks later, > and after considerable use, it's working happily now after I replaced the > blown cap. It must've been a one-off problem, since everything else is still > the same and the new cap went back in the same polarization as the old. Here > is some info on that project btw... > http://www.narwani.org/neil/electronics/mp3/itxpc.html > > Cheers, > -Neil. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist