David Liguori wrote:
Aldo Foot wrote:On Wed, Apr 29, 2009 at 7:23 PM, Robert L Cochran <cochranb speakeasy net> wrote:
One of the more common mechanisms for failure of electrolytic capacitors is too high an ambient temperature over a period of time. Usually the temperature rating is on the cap. You say the room is well-ventilated but that doesn't rule out too high an ambient temperature in a room full of equipment, especially if it was sitting on top of or in a rack full of other equipment. It's more likely to have open rather than short circuited. An ESR (effective series resistance) meter will tell.If you're pretty sure the capacitor is what's ailing it and it's through-hole rather than surface mounted, I would consider it well worth fixing, or even trying if there's greater than a 10% success probability. Many 8-port switches aren't worth fixing below that.
Another issue is using capacitors that are close to the operating voltage of the system. 12V and use 15V capacitors. This doesn't give any overhead for voltage spikes or surges caused by charging and discharging circuits.
Remember that many circuit boards are multi-layer now so be careful if you are working with a thru-hole circuit board.
Have fun. -- Robin Laing