Surface mounted tantalum capacitors
have a stripe printed on the positive side of the part. I prefer to use these
parts in my designs, unless product cost is more important than performance. I
have found that tantalum caps tend to last much longer. But, aluminum
electrolytic capacitors, although cheaper, have the polarity stripe printed on the
negative side of the part. My client was soldering the newer parts in
backwards. Once they flipped the parts around, everything worked fine.